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1.
Arch Pediatr ; 19(6): 585-92, 2012 Jun.
Artigo em Francês | MEDLINE | ID: mdl-22542723

RESUMO

INTRODUCTION: Type 1 diabetes is one of the most frequent chronic diseases in children and adolescents. Self-care support is a crucial aspect of the medical care provided to adolescent patients with type 1 diabetes. In the perspective of health promotion, which seeks to empower people to become the actors of their own health, self-care may be operationalized in three dimensions: psychosocial life, general health, and disease. We looked at the process of autonomization in adolescents 13-15 years of age, and hypothesized that their level of glycemic control (HbA1c) would be related to their perceived level of self-care. PATIENTS AND METHODS: We conducted an exploratory study through 32 in-depth interviews with adolescents aged 13-15 years. The data collected was analyzed quantitatively and qualitatively, based on the annual mean HbA1c level. RESULTS: Significantly higher scores of perceived self-care were associated with levels of HbA1c ≤ 7.5% (P=0.038). Overall, adolescents with good glycemic control reported greater autonomy and complexity in self-care behaviors in all three dimensions of self-care. Moreover, our results show that adolescents with poor glycemic control tend to restrict the definition of self-care to its medical dimension and to exclude the psychosocial dimension. CONCLUSION: Our study confirms the hypothesis of a relation between HbA1c and the self-reported level of self-care in adolescents with type 1 diabetes. Moreover, it emphasizes the need to better respond to the young patients' psychosocial needs, in order to improve the long-term follow-up of adolescents with type 1 diabetes.


Assuntos
Automonitorização da Glicemia , Glicemia/análise , Diabetes Mellitus Tipo 1/sangue , Diabetes Mellitus Tipo 1/terapia , Autocuidado , Adolescente , Feminino , Humanos , Masculino
2.
Rural Remote Health ; 7(4): 840, 2007.
Artigo em Inglês | MEDLINE | ID: mdl-17973595

RESUMO

CONTEXT: Child malaria remains a vital concern in sub-Saharan Africa in spite of major efforts to control it. The widely advertised best curative and preventive measures are not always accessible. ISSUE: This article examines the extent to which parents' perceptions and representations are considered, including their empowerment and participation in interventions aimed at controlling child malaria. The effect of this is examined through a content analysis of articles selected in the PubMed and Wholis databases over the period of 1996 to 2005. This analysis was performed according to three predefined categories consistent with the three main health promotion strategies used in the WHO-AFRO region: (1) development of knowledge and skills; (2) creation of supportive environments; and (3) advocacy. LESSONS LEARNED: Successful interventions met the health promotion strategies wholly or partly. Although these interventions were sometimes incomplete, the development took into account people's perceptions and representations. The authors acted on the belief that empowerment of parents and their participation in the development of interventions to control child malaria, is likely to yield better results and assist in reducing the prevalence of malaria morbidity and mortality in children under 5 years.


Assuntos
Informação de Saúde ao Consumidor/estatística & dados numéricos , Conhecimentos, Atitudes e Prática em Saúde , Malária/prevenção & controle , Pais/educação , África Subsaariana/epidemiologia , Bibliometria , Cuidado da Criança , Pré-Escolar , Participação da Comunidade , Humanos , Lactente , Recém-Nascido , Malária/epidemiologia , Pais/psicologia
5.
Biochem Soc Trans ; 32(Pt 2): 310-3, 2004 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-15046597

RESUMO

Experimental data and in silico analyses of sequenced bacterial genomes indicate that arginine repressor (ArgR) proteins and their respective target sites are surprisingly well conserved in very diverse bacteria. Arginine regulation therefore constitutes an interesting model system from the study of evolutionary aspects of bacterial regulation. Moreover, arginine repressor molecules are multifunctional, they repress the arginine biosynthetic genes and are involved in the activation of the various arginine catabolic pathways. Studies on the arginine repressor from the hyperthermophiles Thermotoga neapolitana and Thermotoga maritima have reinforced the uniform view of the bacterial ArgR-operator interaction, but have also revealed that the Thermotoga repressor exhibits unique features. Thus, its DNA-binding activity is nearly arginine-independent and exhibits poor sequence specificity. ArgR(Tn) has a remarkable capacity to bind heterologous arginine operators and half-site targets.


Assuntos
Arginina/química , Regulação Bacteriana da Expressão Gênica , Thermotoga maritima/metabolismo , Proteínas de Bactérias/química , Sequência de Bases , DNA/química , Genoma Bacteriano , Temperatura Alta , Modelos Biológicos , Dados de Sequência Molecular , Ligação Proteica , Especificidade da Espécie , Thermotoga maritima/genética
6.
J Mol Biol ; 302(2): 411-26, 2000 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-10970742

RESUMO

Escherichia coli PepA is a hexameric aminopeptidase that is also endowed with a DNA-binding activity that functions in transcription control and plasmid dimer resolution. To gain further insight into the functioning of PepA, mutants were selected on the basis of reduced repressibility of a genomic carA-lacZ fusion and studied for the various cellular processes requiring PepA, i.e. repression of the carAB operon, autoregulation, resolution of ColE1 multimers, and peptide proteolysis. The methylation status of the carAB control region was analysed in several pepA mutants and purified proteins were assayed in vitro for car operator DNA binding. This study provides a critical test of predictions advanced on the basis of the structural analysis of PepA and demonstrates the importance for DNA binding of several secondary structural elements in the N-terminal domain and near the very C terminus. By analysis of single amino acid substitutions, we could distinguish the mode of PepA action in car regulation from its action in plasmid resolution. We demonstrate that mere binding of PepA to the car control region is not sufficient to explain its role in pyrimidine-specific regulation; protein-protein interactions appear to play an important role in transcriptional repression. The multifunctional character of PepA and of an increasing number of transcriptional regulators that combine catalytic and regulatory properties, of which several participate in the metabolism of arginine and of the pyrimidines, suggests that enzymes and DNA (RNA) binding proteins fulfilling an essential primeval function may have been recruited in evolution to fulfil an additional regulatory task.


Assuntos
Aminopeptidases/metabolismo , Proteínas de Bactérias , DNA Bacteriano/metabolismo , Proteínas de Ligação a DNA/metabolismo , Dioxigenases , Escherichia coli/enzimologia , Complexos Multienzimáticos/metabolismo , Mutação/genética , Adenina/metabolismo , Aminopeptidases/química , Aminopeptidases/genética , Aminopeptidases/isolamento & purificação , Catálise , Cromossomos Bacterianos/genética , Metilação de DNA , DNA Bacteriano/química , DNA Bacteriano/genética , Proteínas de Ligação a DNA/química , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/isolamento & purificação , Escherichia coli/genética , Escherichia coli/crescimento & desenvolvimento , Retroalimentação , Regulação Bacteriana da Expressão Gênica , Genes Reporter/genética , Glutamil Aminopeptidase , Leucina/metabolismo , Modelos Moleculares , Complexos Multienzimáticos/química , Complexos Multienzimáticos/genética , Complexos Multienzimáticos/isolamento & purificação , Conformação de Ácido Nucleico , Regiões Operadoras Genéticas/genética , Oxigenases/genética , Plasmídeos/química , Plasmídeos/genética , Plasmídeos/metabolismo , Regiões Promotoras Genéticas/genética , Ligação Proteica , Estrutura Secundária de Proteína , Proteínas Repressoras/química , Proteínas Repressoras/genética , Proteínas Repressoras/isolamento & purificação , Proteínas Repressoras/metabolismo , Relação Estrutura-Atividade
7.
J Bacteriol ; 182(13): 3661-72, 2000 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-10850980

RESUMO

Archaea, constituting the third primary domain of life, harbor a basal transcription apparatus of the eukaryotic type, whereas curiously, a large fraction of the potential transcription regulation factors appear to be of the bacterial type. To date, little information is available on these predicted regulators and on the intriguing interplay that necessarily has to occur with the transcription machinery. Here, we focus on Sa-lrp of the extremely thermoacidophilic crenarchaeote Sulfolobus acidocaldarius, encoding an archaeal homologue of the Escherichia coli leucine-responsive regulatory protein Lrp, a global transcriptional regulator and genome organizer. Sa-lrp was shown to produce a monocistronic mRNA that was more abundant in the stationary-growth phase and produced in smaller amounts in complex medium, this down regulation being leucine independent. We report on Sa-Lrp protein purification from S. acidocaldarius and from recombinant E. coli, both identified by N-terminal amino acid sequence determination. Recombinant Sa-Lrp was shown to be homotetrameric and to bind to its own control region; this binding proved to be leucine independent and was stimulated at high temperatures. Interference binding experiments suggested an important role for minor groove recognition in the Sa-Lrp-DNA complex formation, and mutant analysis indicated the importance for DNA binding of the potential helix-turn-helix motif present at the N terminus of Sa-Lrp. The DNA-binding capacity of purified Sa-Lrp was found to be more resistant to irreversible heat inactivation in the presence of L-leucine, suggesting a potential physiological role of the amino acid as a cofactor.


Assuntos
Proteínas Arqueais/metabolismo , Proteínas de Ligação a DNA/metabolismo , Sulfolobus acidocaldarius/metabolismo , Fatores de Transcrição/metabolismo , Substituição de Aminoácidos , Proteínas Arqueais/genética , Proteínas Arqueais/isolamento & purificação , Sequência de Bases , DNA/metabolismo , Pegada de DNA , DNA Arqueal , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/isolamento & purificação , Desoxirribonuclease I , Escherichia coli , Proteínas de Escherichia coli , Expressão Gênica , Genes , Sequências Hélice-Alça-Hélice , Proteína Reguladora de Resposta a Leucina , Ligantes , Dados de Sequência Molecular , Regiões Operadoras Genéticas , RNA Arqueal , RNA Mensageiro , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/isolamento & purificação , Proteínas Recombinantes de Fusão/metabolismo , Sulfolobus acidocaldarius/genética , Temperatura , Fatores de Transcrição/genética , Fatores de Transcrição/isolamento & purificação
8.
J Mol Evol ; 49(4): 461-73, 1999 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-10486004

RESUMO

Forty-four sequences of ornithine carbamoyltransferases (OTCases) and 33 sequences of aspartate carbamoyltransferases (ATCases) representing the three domains of life were multiply aligned and a phylogenetic tree was inferred from this multiple alignment. The global topology of the composite rooted tree (each enzyme family being used as an outgroup to root the other one) suggests that present-day genes are derived from paralogous ancestral genes which were already of the same size and argues against a mechanism of fusion of independent modules. A closer observation of the detailed topology shows that this tree could not be used to assess the actual order of organismal descent. Indeed, this tree displays a complex topology for many prokaryotic sequences, with polyphyly for Bacteria in both enzyme trees and for the Archaea in the OTCase tree. Moreover, representatives of the two prokaryotic Domains are found to be interspersed in various combinations in both enzyme trees. This complexity may be explained by assuming the occurrence of two subfamilies in the OTCase tree (OTC alpha and OTC beta) and two other ones in the ATCase tree (ATC I and ATC II). These subfamilies could have arisen from duplication and selective losses of some differentiated copies during the successive speciations. We suggest that Archaea and Eukaryotes share a common ancestor in which the ancestral copies giving the present-day ATC II/OTC beta combinations were present, whereas Bacteria comprise two classes: one containing the ATC II/OTC alpha combination and the other harboring the ATC I/OTC beta combination. Moreover, multiple horizontal gene transfers could have occurred rather recently amongst prokaryotes. Whichever the actual history of carbamoyltransferases, our data suggest that the last common ancestor to all extant life possessed differentiated copies of genes coding for both carbamoyltransferases, indicating it as a rather sophisticated organism.


Assuntos
Aspartato Carbamoiltransferase/genética , Evolução Molecular , Ornitina Carbamoiltransferase/genética , Sequência de Aminoácidos , Bases de Dados Factuais , Modelos Genéticos , Dados de Sequência Molecular , Filogenia , Alinhamento de Sequência , Homologia de Sequência de Aminoácidos
9.
J Mol Biol ; 291(4): 843-55, 1999 Aug 27.
Artigo em Inglês | MEDLINE | ID: mdl-10452892

RESUMO

Recently the crystal structure of the DNA-unbound form of the full-length hexameric Bacillus stearothermophilus arginine repressor (ArgR) has been resolved, providing a possible explanation for the mechanism of arginine-mediated repressor-operator DNA recognition. In this study we tested some of these functional predictions by performing site-directed mutagenesis of distinct amino acid residues located in two regions, the N-terminal DNA-binding domain and the C-terminal oligomerization domain of ArgR. A total of 15 mutants were probed for their capacity to repress the expression of the reporter argC - lacZ gene fusion in Escherichia coli cells. Substitutions of highly conserved amino acid residues in the alpha2 and alpha3 helices, located in the winged helix-turn-helix DNA-binding motif, reduced repression. Loss of DNA-binding capacity was confirmed in vitro for the Ser42Pro mutant which showed the most pronounced effect in vivo. In E. coli, the wild-type B. stearothermophilus ArgR molecule behaves as a super-repressor, since recombinant E. coli host cells bearing B. stearothermophilusargR on a multicopy vector did not grow in selective minimal medium devoid of arginine and grew, albeit weakly, when l -arginine was supplied. All mutants affected in the DNA-binding domain lost this super-repressor behaviour. Replacements of conserved leucine residues at positions 87 and/or 94 in the C-terminal domain by other hydrophobic amino acid residues proved neutral or caused either derepression or stronger super-repression. Substitution of Leu87 by phenylalanine was found to increase the DNA-binding affinity and the protein solubility in the context of a double Leu87Phe/Leu94Val mutant. Structural modifications occasioned by the various amino acid substitutions were confirmed by circular dichroism analysis and structure modelling.


Assuntos
Proteínas de Bactérias , DNA Bacteriano/metabolismo , Proteínas de Escherichia coli , Geobacillus stearothermophilus/genética , Geobacillus stearothermophilus/metabolismo , Proteínas Repressoras/química , Proteínas Repressoras/genética , Sequência de Aminoácidos , Sequência de Bases , Sítios de Ligação/genética , Dicroísmo Circular , Sequência Conservada , Primers do DNA/genética , Estabilidade de Medicamentos , Escherichia coli/genética , Modelos Moleculares , Dados de Sequência Molecular , Mutagênese Sítio-Dirigida , Mutação Puntual , Conformação Proteica , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Proteínas Repressoras/metabolismo , Homologia de Sequência de Aminoácidos , Temperatura
10.
Eur J Biochem ; 264(1): 233-41, 1999 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-10447693

RESUMO

The genes coding for aspartate carbamoyltransferase (ATCase) in the extremely thermophilic archaeon Sulfolobus acidocaldarius have been cloned by complementation of a pyrBI deletion mutant of Escherichia coli. Sequencing revealed the existence of an enterobacterial-like pyrBI operon encoding a catalytic chain of 299 amino acids (34 kDa) and a regulatory chain of 170 amino acids (17.9 kDa). The deduced amino acid sequences of the pyrB and pyrI genes showed 27.6-50% identity with archaeal and enterobacterial ATCases. The recombinant S. acidocaldarius ATCase was purified to homogeneity, allowing the first detailed studies of an ATCase isolated from a thermophilic organism. The recombinant enzyme displayed the same properties as the ATCase synthesized in the native host. It is highly thermostable and exhibits Michaelian saturation kinetics for carbamoylphosphate (CP) and positive homotropic cooperative interactions for the binding of L-aspartate. Moreover, it is activated by nucleoside triphosphates whereas the catalytic subunits alone are inhibited. The holoenzyme purified from recombinant E. coli cells or present in crude extract of the native host have an Mr of 340 000 as estimated by gel filtration, suggesting that it has a quaternary structure similar to that of E. coli ATCase. Only monomers could be found in extracts of recombinant E. coli or Saccharomyces cerevisiae cells expressing the pyrB gene alone. In the presence of CP these monomers assembled into trimers. The stability of S. acidocaldarius ATCase and the allosteric properties of the enzyme are discussed in function of a modeling study.


Assuntos
Aspartato Carbamoiltransferase/genética , Sulfolobus acidocaldarius/enzimologia , Regulação Alostérica , Sequência de Aminoácidos , Aspartato Carbamoiltransferase/isolamento & purificação , Aspartato Carbamoiltransferase/metabolismo , Sequência de Bases , Clonagem Molecular , Primers do DNA , Estabilidade Enzimática , Escherichia coli/genética , Temperatura Alta , Cinética , Modelos Químicos , Dados de Sequência Molecular , Peso Molecular , Homologia de Sequência de Aminoácidos
11.
Nat Struct Biol ; 6(5): 427-32, 1999 May.
Artigo em Inglês | MEDLINE | ID: mdl-10331868

RESUMO

The arginine repressor (ArgR) is a hexameric DNA-binding protein that plays a multifunctional role in the bacterial cell. Here, we present the 2.5 A structure of apo-ArgR from Bacillus stearothermophilus and the 2.2 A structure of the hexameric ArgR oligomerization domain with bound arginine. This first view of intact ArgR reveals an approximately 32-symmetric hexamer of identical subunits, with six DNA-binding domains surrounding a central oligomeric core. The difference in quaternary organization of subunits in the arginine-bound and apo forms provides a possible explanation for poor operator binding by apo-ArgR and for high affinity binding in the presence of arginine.


Assuntos
Proteínas de Bactérias/química , Geobacillus stearothermophilus/química , Proteínas Repressoras/química , Sequência de Aminoácidos , Arginina/química , Arginina/metabolismo , Arginina/farmacologia , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Sítios de Ligação , Cristalização , Cristalografia por Raios X , Proteínas de Ligação a DNA/química , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Geobacillus stearothermophilus/genética , Modelos Moleculares , Dados de Sequência Molecular , Regiões Operadoras Genéticas/genética , Fragmentos de Peptídeos/química , Fragmentos de Peptídeos/genética , Fragmentos de Peptídeos/metabolismo , Ligação Proteica/efeitos dos fármacos , Conformação Proteica/efeitos dos fármacos , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Proteínas Repressoras/genética , Proteínas Repressoras/metabolismo , Solventes
12.
J Mol Biol ; 286(4): 1217-28, 1999 Mar 05.
Artigo em Inglês | MEDLINE | ID: mdl-10047492

RESUMO

Escherichia coli carbamoylphosphate synthetase (CPSase) is a key enzyme in the pyrimidine nucleotides and arginine biosynthetic pathways. The enzyme harbors a complex regulation, being activated by ornithine and inosine 5'-monophosphate (IMP), and inhibited by UMP. CPSase mutants obtained by in vivo mutagenesis and selected on the basis of particular phenotypes have been characterized kinetically. Two residues, serine 948 and threonine 1042, appear crucial for allosteric regulation of CPSase. When threonine 1042 is replaced by an isoleucine residue, the enzyme displays a greatly reduced activation by ornithine. The T1042I mutated enzyme is still sensitive to UMP and IMP, although the effects of both regulators are reduced. When serine 948 is replaced by phenylalanine, the enzyme becomes insensitive to UMP and IMP, but is still activated by ornithine, although to a reduced extent. When correlating these observations to the structural data recently reported, it becomes clear that both mutations, which are located in spatially distinct regions corresponding respectively to the ornithine and the UMP/IMP binding sites, have coupled effects on the enzyme regulation. These results provide an illustration that coupling of regulatory pathways occurs within the allosteric subunit of E. coli CPSase. In addition, other mutants have been characterized, which display altered affinities for the different CPSase substrates and also slightly modified properties towards the allosteric effectors: P165S, P170L, A182V, P360L, S743N, T800F and G824D. Kinetic properties of these modified enzymes are also presented here and correlated to the crystal structure of E. coli CPSase and to the phenotype of the mutants.


Assuntos
Carbamoil Fosfato Sintase (Glutamina-Hidrolizante)/metabolismo , Escherichia coli/enzimologia , Serina/metabolismo , Treonina/metabolismo , Regulação Alostérica , Arginina/farmacologia , Carbamoil Fosfato Sintase (Glutamina-Hidrolizante)/química , Clonagem Molecular , DNA Bacteriano/análise , Cinética , Modelos Moleculares , Mutação , Fenótipo , Conformação Proteica , Uracila/farmacologia
13.
J Mol Biol ; 280(4): 571-82, 1998 Jul 24.
Artigo em Inglês | MEDLINE | ID: mdl-9677289

RESUMO

The carAB operon of the enterics Escherichia coli K-12 and Salmonella typhimurium LT2, encoding the sole carbamoylphosphate synthetase (CPSase) of these organisms, is transcribed from two promoters in tandem, carP1 upstream and carP2 downstream, repressed respectively by pyrimidines and arginine. We present evidence that the pyrH gene product (the hexameric UMP-kinase) directly participates in the pyrimidine-specific control of carP1 activity. Indeed, we have isolated in E. coli a particular type of pyrH mutation (pyrH41) that retains a quasi-normal UMP-kinase activity, but yet is impaired in the pyrimidine-specific repression of the P1 promoter of the carAB operon of E. coli and of S. typhimurium. Moreover, the pyrimidine-dependent inhibition of in vivo Dam methylase modification of adenine -106 upstream of the carP1 promoter is altered in this pyrH mutant. The recessive pyrH41 allele bears a single C-G to A-T transversion that converts alanine 94 into glutamic acid (A94E). Although overexpression of pyrH41 results in UMP-kinase levels far above that of a wild-type strain, pyrimidine-specific repression of the carAB operon is not restored under these conditions. Similarly, overexpression of the UMP-CMP-kinase gene of Dictyostelium discoideum in the pyrH41 mutant does not restore pyrimidine-mediated control of carP1 promoter activity, in spite of the elevated UMP-kinase activity measured in such transformants. These results indicate that besides its catalytic function in the de novo pyrimidine biosynthesis, E. coli UMP-kinase fulfils an additional, but previously unrecognized role in the regulation of the carAB operon. UMP-kinase might function as the real sensor of the internal pyrimidine nucleotide pool and act in concert with the integration host factor (IHF) and aminopeptidase A (PepA alias CarP and XerB) in the elaboration of the complex nucleoprotein structure required for pyrimidine-specific repression of carP1 promoter activity.


Assuntos
Proteínas de Bactérias/genética , Escherichia coli/genética , Núcleosídeo-Fosfato Quinase/genética , Regiões Promotoras Genéticas/genética , Adenina/química , Proteínas de Bactérias/metabolismo , Metilação de DNA , Escherichia coli/enzimologia , Regulação Bacteriana da Expressão Gênica , Mutação/genética , Núcleosídeo-Fosfato Quinase/metabolismo , Pirimidinas/metabolismo , Salmonella typhimurium/genética , Ativação Transcricional
14.
J Mol Biol ; 277(4): 805-24, 1998 Apr 10.
Artigo em Inglês | MEDLINE | ID: mdl-9545374

RESUMO

In order to gain further insight into the molecular mechanism of arginine-dependent operator recognition by the hexameric Escherichia coli arginine repressor we have probed protein-DNA interactions in vitro and in vivo. We have extensively applied the chemical modification-protection and premodification-interference approach to two operators, the natural operator overlapping the P2 promoter of the carAB operon and a fully symmetrical consensus sequence. Backbone contacts were revealed by hydroxyl radical footprinting and phosphate ethylation interference. Base-specific contacts to purines and pyrimidines were revealed by methylation protection and premodification interference, KMnO4 and NH2OH.HCl-specific modification of thymine and cytosine residues, base-removal (depurination and depyrimidation), and base substitution (uracil and inosine). Additional information on the groove specificity of repressor binding was obtained by small ligand binding interference (distamycin and methyl green). In vivo, we measured the effects on the repressibility of 24 single base-pair substitutions obtained by saturation mutagenesis of half an Arg box in the carAB operator. The results of these experiments point to the conclusion that a hexameric arginine repressor molecule covers four turns of the helix, makes base-specific contacts to at least one guanine (G4 or G4') and two thymine (T3, T13', or T3', T13) residues in each one of four consecutive major grooves on one face of the helix and with four A-T/T-A base-pairs, comprising the adenine residues A9, 9', 12, 12' and the thymine residues T10, 10', 11, 11', in the two outermost minor grooves of the operator, on the very same face of the DNA molecule. The hydrophobic 5-methyl groups of four thymine residues (T3, 3', 13, 13') in each Arg box contribute to major groove-specific recognition via hydrophobic and/or van der Waals interactions. The importance of minor groove contacts was further supported by the drastic effect of distamycin binding interference. In vivo, the most pronounced drops in repressibility were occasioned by mutations at positions 10 (A-->G or C), 11 (T-->A or G) and 12 (A-->G, T or C).


Assuntos
Proteínas de Bactérias , DNA Bacteriano/genética , DNA Bacteriano/metabolismo , Proteínas de Escherichia coli , Escherichia coli/genética , Escherichia coli/metabolismo , Regiões Operadoras Genéticas , Proteínas Repressoras/metabolismo , Arginina/metabolismo , Composição de Bases , Sequência de Bases , Sítios de Ligação/genética , Sequência Consenso , DNA Bacteriano/química , Modelos Moleculares , Dados de Sequência Molecular , Mutagênese Sítio-Dirigida , Conformação de Ácido Nucleico , Ligação Proteica , Purinas/metabolismo , Pirimidinas/metabolismo
15.
Gene ; 201(1-2): 63-8, 1997 Nov 12.
Artigo em Inglês | MEDLINE | ID: mdl-9409772

RESUMO

The lrp gene of the extreme thermophilic archaeon Sulfolofus solfataricus, encoding a homologue of the eubacterial global leucine-responsive regulatory protein, was identified by DNA sequencing and sequence comparisons on a 6.9-kb genomic fragment cloned into Escherichia coli. The S. solfataricus Lrp subunit is a 155-aa polypeptide that bears between 24.5 and 29% sequence identity with eubacterial regulatory proteins of the Lrp/AsnC family and 30.6% and 25.8% with the archaeal homologues of respectively Methanococcus jannaschii and Pyrococcus furiosus. Transcription initiation from the strong S. solfataricus lrp promoter was analyzed by primer extension mapping. The abundance of the S. solfataricus lrp messenger strongly suggests that this protein might function in archaea as a global transcriptional regulator and genome organizer, as proposed for E. coli Lrp, rather than as a local, specific regulatory protein. Our findings suggest the presence of a eubacterial type of regulatory mechanism in archaea, a situation that is noteworthy indeed, since the transcriptional machinery of archaea is more closely related to that of eukaryotes, whereas these latter apparently do not possess a homologue of Lrp.


Assuntos
Proteínas Arqueais/genética , Genes Arqueais , Leucina , Sulfolobus/genética , Fatores de Transcrição/genética , Sequência de Aminoácidos , Sequência de Bases , Clonagem Molecular , DNA Arqueal , Proteínas de Ligação a DNA , Proteínas de Escherichia coli , Proteína Reguladora de Resposta a Leucina , Dados de Sequência Molecular , Homologia de Sequência de Aminoácidos , Transcrição Gênica
16.
Mol Microbiol ; 25(2): 385-98, 1997 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-9282750

RESUMO

We report here the cloning of the arginine repressor gene argR of Bacillus stearothermophilus and the characterization and purification to homogeneity of its product. The deduced amino acid sequence of the 16.8-kDa ArgR subunit shares 72% identity with its mesophilic homologue AhrC of Bacilus subtilis. Sequence analysis of B. stearothermophilus ArgR and comparisons with mesophilic arginine repressors suggest that the thermostable repressor comprises an N-terminal DNA-binding and a C-terminal oligomerization and arginine-binding region. B. stearothermophilus ArgR has been overexpressed in E. coli and purified as a 48.0-kDa trimeric protein. The repressor inhibits the expression of a B. stearothermophilus argC-lacZ fusion in E. coli cells. In the presence of arginine, the purified protein binds tightly and specifically to the argC operator, which largely overlaps the argC promoter. The purified B. stearothermophilus repressor proved to be very thermostable with a half-life of approximately 30 min at 90 degrees C, whereas B. subtilis AhrC was largely inactivated at 65 degrees C. Moreover, ArgR operator complexes were found to be remarkably thermostable and could be formed efficiently at up to 85 degrees C, well above the optimal growth temperature of the moderate thermophile B. stearothermophilus. This pronounced resistance of the repressor-operator complexes to heat treatment suggests that the same type of regulatory mechanism could operate in extreme thermophiles.


Assuntos
Proteínas de Bactérias/genética , Genes Bacterianos , Geobacillus stearothermophilus/genética , Proteínas Repressoras/genética , Sequência de Aminoácidos , Sequência de Bases , Clonagem Molecular , Temperatura Alta , Dados de Sequência Molecular , Análise de Sequência de DNA
17.
Mol Gen Genet ; 252(1-2): 69-78, 1996 Aug 27.
Artigo em Inglês | MEDLINE | ID: mdl-8804405

RESUMO

Mechanisms of gene regulation have not yet been extensively studied in thermophilic bacteria. In previous studies we showed that the Bacillus stearothermophilus argCJBD gene cluster is subject to specific repression by arginine. Here we report the cloning by colony hybridization, and characterization of the proximal part of the argC gene together with the adjacent control region of the cluster. The promoter was identified by primer extension mapping of the argC transcription startpoint: a sequence overlapping it was found to be similar to the arginine operators of B. subtilis and to a smaller extent of E. coli. Use of an argC-lacZ gene fusion revealed that the argC promoter is strongly repressed by the heterologous B. subtilis arginine repressor/activator AhrC in E. coli cells. Mobility shift and DNase I footprinting experiments revealed tight, specific and arginine-dependent binding of this operator-like sequence to purified AhrC. It is therefore very likely that in B. stearothermophilus the expression of the argCJBD operon is modulated by a repressor that is the thermophilic homologue of AhrC.


Assuntos
Arginina/biossíntese , Bacillus subtilis/genética , Proteínas de Bactérias , Proteínas de Escherichia coli , Geobacillus stearothermophilus/genética , Óperon/genética , Proteínas Repressoras/metabolismo , Sequência de Aminoácidos , Sequência de Bases , Clonagem Molecular , Pegada de DNA , DNA Recombinante , Escherichia coli/genética , Regulação Bacteriana da Expressão Gênica , Dados de Sequência Molecular , Regiões Operadoras Genéticas/genética , Regiões Promotoras Genéticas/genética , Proteínas Repressoras/genética , Mapeamento por Restrição , Análise de Sequência de DNA , Transformação Bacteriana
18.
J Mol Biol ; 250(4): 383-91, 1995 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-7616563

RESUMO

By measuring the protection against Dam methylase modification of a GATC sequence located 106 bp upstream of the startpoint of promoter P1 in the control region of the carAB operon (encoding carbamoylphosphate synthetase) we have obtained evidence for a direct correlation between the degree of in vivo occupancy of a specific regulatory target site and the repressibility of the P1 promoter by pyrimidine residues. A high uridine nucleotide pool as well as binding of the carP (alias xerB/pepA) gene product and of the integration host factor (IHF) to the carAB control region are prerequisites to observe this in vivo protection. Purified CarP binds in vitro to the carAB control region and protects against DNase I two approximately 25 bp long stretches, one of which is located just downstream of the GATC sequence. Mutations in this site strongly impair the pyrimidine regulation of the P1 promoter and the interference with Dam methylase modification. These processes are also strongly impaired in the absence of integration host factor and in mutants affected in the IHF site located some 200 bp upstream of this Dam methylase modification site. IHF therefore exerts at least part of its antagonistic effects on P1, i.e. increased expression in minimal medium but increased repression in the presence of pyrimidine residues, indirectly by influencing the formation or the stability of a particular protein-DNA complex. Furthermore, we demonstrate that the distance separating the IHF and Dam methylase target sites is crucial for the in vivo protection and for pyrimidine-mediated regulation of the promoter expression. Mutations altering this distance result in severe reductions of the degree of in vivo protection and, concomitantly, of the repressibility by pyrimidine residues of promoter P1 activity in a way indicative of the formation of a complex nucleoprotein structure. Since neither IHF nor CarP require pyrimidine residues to bind to the carAB control region, at least not in vitro, it is tempting to suggest that IHF and CarP-induced bending and looping provide changes in DNA topology that are required for assembling a specific pyrimidine-dependent nucleoprotein complex that modulates P1 activity.


Assuntos
Aminopeptidases/metabolismo , Proteínas de Bactérias/metabolismo , Carbamoil Fosfato Sintase (Glutamina-Hidrolizante)/genética , Regiões Promotoras Genéticas , Pirimidinas/metabolismo , DNA Metiltransferases Sítio Específica (Adenina-Específica)/metabolismo , Adenina/metabolismo , Aminopeptidases/genética , Animais , Proteínas de Bactérias/genética , Sequência de Bases , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Desoxirribonuclease I/metabolismo , Escherichia coli/genética , Escherichia coli/metabolismo , Proteínas de Escherichia coli , Glutamil Aminopeptidase , Fatores Hospedeiros de Integração , Metilação , Dados de Sequência Molecular , Mutação , Óperon/genética , Proteínas Repressoras/genética , Proteínas Repressoras/metabolismo , Salmonella typhimurium/genética , Salmonella typhimurium/metabolismo , Transcrição Gênica/genética , Nucleotídeos de Uracila/genética , Nucleotídeos de Uracila/metabolismo
19.
J Mol Biol ; 250(4): 392-406, 1995 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-7616564

RESUMO

The carP gene involved in pyrimidine-specific regulation of the upstream P1 promoter of the Escherichia coli carAB operon has been cloned in vivo on a mini-Mu replicon, sequenced and shown to be identical to the xerB (pepA) gene encoding aminopeptidase A, a protein also involved in the Xer-mediated site-specific recombination at ColEI cer. The trans-dominant allele carP6 was cloned as well and shown to bear a single G-->A transition that converts the TGG codon (Trp473) into a TAG amber stop codon. The truncated mutant protein, missing the 31 C-terminal amino acid residues, was shown to be partially active; in the multicopy state the carP6 allele can restore pyrimidine repressibility of the carAB promoter P1. The trans-dominant character of the single copy carP6 allele was found to be suppressed in the presence of multiple copies of the wild-type gene. The carP (pepA) control region was sequenced and transcription shown to be initiated at three promoters, the most upstream one of which was shown to be subject to negative autoregulation. The aminopeptidase activity of CarP (PepA) was found to be dispensable for its role in pyrimidine-mediated repression of carAB transcription. CarP (PepA) was shown to be a sequence-specific DNA-binding protein that does not require, at least not in vitro, any pyrimidine cofactor to bind to the DNA. Mobility-shift and DNase I footprinting experiments have revealed a specific binding of purified CarP (PepA) to two sites in each one of the control regions of the E. coli and Salmonella typhimurium carAB operons and to a single site in the carP (pepA) control region. We propose that integration host factor and CarP/PepA-induced structural modifications in the carAB control region cause conformational changes required to assemble a pyrimidine-specific nucleo-protein regulatory complex.


Assuntos
Aminopeptidases/genética , Carbamoil Fosfato Sintase (Glutamina-Hidrolizante)/genética , Proteínas de Ligação a DNA/genética , Proteínas de Escherichia coli , Escherichia coli/genética , Regulação Bacteriana da Expressão Gênica , Integrases , Sequência de Aminoácidos , Aminopeptidases/química , Aminopeptidases/isolamento & purificação , Aminopeptidases/metabolismo , Proteínas de Bactérias/genética , Plasmídeos de Bacteriocinas , Sequência de Bases , Mapeamento Cromossômico , Clonagem Molecular , DNA Nucleotidiltransferases/genética , DNA Nucleotidiltransferases/metabolismo , Proteínas de Ligação a DNA/química , Proteínas de Ligação a DNA/isolamento & purificação , Proteínas de Ligação a DNA/metabolismo , Escherichia coli/enzimologia , Glutamil Aminopeptidase , Dados de Sequência Molecular , Mutação , Óperon/genética , Regiões Promotoras Genéticas/genética , Pirimidinas/metabolismo , Recombinases , Recombinação Genética/genética , Proteínas Repressoras/genética , Análise de Sequência , Transcrição Gênica/genética
20.
Arch Pediatr ; 2(6): 589-94, 1995 Jun.
Artigo em Francês | MEDLINE | ID: mdl-7543792

RESUMO

The authors report on their experience of the integrated medical and psychological care in a pediatric intensive care unit. They describe an individualized psychological management of the child at high risk of imminent death. The helpful attitudes and people are identified such as a loving human presence, a climate of trust, life openness and tolerance to child's reactions and receptiveness to the still present life. With the provided support, the child possibly goes through his difficult experience in a more serene way, at his own rythm, with the respect and the acceptance for his individual expression.


Assuntos
Morte , Assistência Terminal , Atitude do Pessoal de Saúde , Atitude Frente a Morte , Criança , Pré-Escolar , Humanos , Unidades de Terapia Intensiva Pediátrica , Cuidados Paliativos , Pais/psicologia , Psicoterapia , Fatores de Risco
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