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1.
Tob Control ; 15(2): 140-2, 2006 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-16565464

RESUMO

BACKGROUND: Evidence indicates that point of purchase (POP) advertising and promotions for cigarettes have increased since the Master Settlement Agreement (MSA). Retail promotions have the potential to offset the effects of cigarette tax and price increases and tobacco control programmes. OBJECTIVE: To describe the trend in the proportion of cigarette sales that occur as part of a POP promotion before and after the MSA. DESIGN: Scanner data were analysed on cigarette sales from a national sample of grocery stores, reported quarterly from 1994 through 2003. The proportion of total cigarette sales that occurred under any of three different types of POP promotions is presented. RESULTS: The proportion of cigarettes sold under a POP promotion increased notably over the sample period. Large increases in promoted sales are observed following implementation of the MSA and during periods of sustained cigarette excise tax increases. CONCLUSIONS: The observed pattern of promoted cigarette sales is suggestive of a positive relationship between retail cigarette promotions, the MSA, and state cigarette tax increases. More research is needed to describe fully the relationship between cigarette promotions and tobacco control policy.


Assuntos
Marketing/métodos , Indústria do Tabaco/métodos , Publicidade/métodos , Comércio , Humanos , Prevenção do Hábito de Fumar , Impostos , Estados Unidos
2.
Proc Natl Acad Sci U S A ; 98(20): 11411-6, 2001 Sep 25.
Artigo em Inglês | MEDLINE | ID: mdl-11553768

RESUMO

Sequence analysis of a 10-kb region of the genome of the marine cyanomyovirus S-PM2 reveals a homology to coliphage T4 that extends as a contiguous block from gene (g)18 to g23. The order of the S-PM2 genes in this region is similar to that of T4, but there are insertions and deletions of small ORFs of unknown function. In T4, g18 codes for the tail sheath, g19, the tail tube, g20, the head portal protein, g21, the prohead core protein, g22, a scaffolding protein, and g23, the major capsid protein. Thus, the entire module that determines the structural components of the phage head and contractile tail is conserved between T4 and this cyanophage. The significant differences in the morphology of these phages must reflect the considerable divergence of the amino acid sequence of their homologous virion proteins, which uniformly exceeds 50%. We suggest that their enormous diversity in the sea could be a result of genetic shuffling between disparate phages mediated by such commonly shared modules. These conserved sequences could facilitate genetic exchange by providing partially homologous substrates for recombination between otherwise divergent phage genomes. Such a mechanism would thus expand the pool of phage genes accessible by recombination to all those phages that share common modules.


Assuntos
Colífagos/genética , Corticoviridae/genética , Sequência de Bases , Evolução Biológica , Primers do DNA , Eletroforese em Gel de Campo Pulsado , Dados de Sequência Molecular , Filogenia , Reação em Cadeia da Polimerase , Água do Mar/virologia , Vírion/genética
3.
FEBS Lett ; 479(1-2): 72-7, 2000 Aug 11.
Artigo em Inglês | MEDLINE | ID: mdl-10940391

RESUMO

The Synechocystis sp. PCC 6803 genome encodes four putative homologues of the AAA protease FtsH, two of which (slr0228 and sll1463) have been subjected to insertional mutagenesis in this study. Disruption of sll1463 had no discernible effect but disruption of slr0228 caused a 60% reduction in the abundance of functional photosystem I, without affecting the cellular content of photosystem II or phycobilisomes. Fluorescence and immunoblotting analyses show reductions in PS I polypeptides and possible structural alterations in the residual PS I, indicating an important role for slr0228 in PS I biogenesis.


Assuntos
Proteínas de Bactérias/química , Proteínas de Bactérias/metabolismo , Cianobactérias/metabolismo , Proteínas de Membrana/química , Proteínas de Membrana/metabolismo , Complexo de Proteínas do Centro de Reação Fotossintética/química , Complexo de Proteínas do Centro de Reação Fotossintética/metabolismo , Proteases Dependentes de ATP , Sequência de Aminoácidos , Proteínas de Bactérias/genética , Sequência de Bases , Cianobactérias/genética , Primers do DNA/genética , Escherichia coli/genética , Proteínas de Escherichia coli , Genoma Bacteriano , Proteínas de Membrana/genética , Dados de Sequência Molecular , Mutagênese Insercional , Fases de Leitura Aberta , Complexo de Proteínas do Centro de Reação Fotossintética/genética , Ficobilissomas , Homologia de Sequência de Aminoácidos
4.
Comput Biol Med ; 30(5): 287-98, 2000 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-10913774

RESUMO

The goal of this research was to examine methods of automatically scoring patient pain drawings. Two hundred and fifty pain drawings were selected from the files of an orthopaedic surgeon who specializes in the treatment of low back pain patients. An artificial neural network was designed to score these drawings. The drawings were segmented into 85 regions following dermatomal mappings and from these regions the percent area in pain in each was computed and used as the neural network input variables. With five outcome categories (scores) we obtained a classification sensitivity of 49%, which is approximately as well as physician experts and discriminant analysis achieved using a subset of the same data. We conclude that an artificial neural network is well suited to automatically score patient pain drawings.


Assuntos
Dor Lombar/fisiopatologia , Redes Neurais de Computação , Medição da Dor/métodos , Humanos , Processamento de Imagem Assistida por Computador/métodos , Dor Lombar/classificação , Ilustração Médica , Medição da Dor/estatística & dados numéricos
5.
Appl Environ Microbiol ; 64(6): 2051-60, 1998 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-9603813

RESUMO

Viruses are ubiquitous components of marine ecosystems and are known to infect unicellular phycoerythrin-containing cyanobacteria belonging to the genus Synechococcus. A conserved region from the cyanophage genome was identified in three genetically distinct cyanomyoviruses, and a sequence analysis revealed that this region exhibited significant similarity to a gene encoding a capsid assembly protein (gp20) from the enteric coliphage T4. The results of a comparison of gene 20 sequences from three cyanomyoviruses and T4 allowed us to design two degenerate PCR primers, CPS1 and CPS2, which specifically amplified a 165-bp region from the majority of cyanomyoviruses tested. A competitive PCR (cPCR) analysis revealed that cyanomyovirus strains could be accurately enumerated, and it was demonstrated that quantification was log-linear over ca. 3 orders of magnitude. Different calibration curves were obtained for each of the three cyanomyovirus strains tested; consequently, cPCR performed with primers CPS1 and CPS2 could lead to substantial inaccuracies in estimates of phage abundance in natural assemblages. Further sequence analysis of cyanomyovirus gene 20 homologs would be necessary in order to design primers which do not exhibit phage-to-phage variability in priming efficiency. It was demonstrated that PCR products of the correct size could be amplified from seawater samples following 100x concentration and even directly without any prior concentration. Hence, the use of degenerate primers in PCR analyses of cyanophage populations should provide valuable data on the diversity of cyanophages in natural assemblages. Further optimization of procedures may ultimately lead to a sensitive assay which can be used to analyze natural cyanophage populations both quantitatively (by cPCR) and qualitatively following phylogenetic analysis of amplified products.


Assuntos
Bacteriófago T4/genética , Bacteriófagos/genética , Proteínas do Capsídeo , Capsídeo/genética , Cianobactérias/virologia , Reação em Cadeia da Polimerase/métodos , Sequência de Aminoácidos , Bacteriófagos/classificação , Bacteriófagos/isolamento & purificação , Sequência de Bases , Primers do DNA/genética , DNA Viral/genética , Genoma Viral , Dados de Sequência Molecular , Myoviridae/classificação , Myoviridae/genética , Myoviridae/isolamento & purificação , Podoviridae/classificação , Podoviridae/genética , Podoviridae/isolamento & purificação , Homologia de Sequência de Aminoácidos , Homologia de Sequência do Ácido Nucleico , Especificidade da Espécie
6.
J Spinal Disord ; 11(1): 29-35, 1998 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-9493767

RESUMO

Health care practitioners believe that patient education enhances patients' compliance with treatment, their medical outcomes, and their quality of life. This study evaluated an existing method of noncomputerized structured preoperative education delivered by a nurse specialist and implemented and evaluated a computer-assisted instruction (CAI) tool for nonsurgical patients in the Vanderbilt Orthopaedic Spine Service. These patient education modalities were assessed with regard to the patient health concepts measured in the Short Form-36 Health Survey and, in addition, for preoperative education, with regard to the length of patient hospital stay. Preoperative education improved patient perceptions of vitality and mental health, increased length of stay for discectomy patients, and had no effect on length of stay for other surgical procedures. CAI improved patient perceptions of bodily pain.


Assuntos
Instrução por Computador/métodos , Educação de Pacientes como Assunto/métodos , Cuidados Pré-Operatórios/métodos , Doenças da Coluna Vertebral/cirurgia , Discotomia , Estudos de Avaliação como Assunto , Humanos , Laminectomia , Avaliação de Resultados em Cuidados de Saúde , Satisfação do Paciente , Doenças da Coluna Vertebral/psicologia
7.
Appl Environ Microbiol ; 63(6): 2411-20, 1997 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-9172363

RESUMO

In the marine cyanobacterium Synechococcus sp. strain WH7803, PstS is a 32-kDa cell wall-associated phosphate-binding protein specifically synthesized under conditions of restricted inorganic phosphate (P1) availability (D. J. Scanlan, N. H. Mann, and N. G. Carr, Mol. Microbiol. 10:181-191, 1993). We have assessed its use as a potential diagnostic marker for the P status of photosynthetic picoplankton. Expression of PstS in Synechococcus sp. strain WH7803 was observed when the P1 concentration fell below 50 nM, demonstrating that the protein is induced at concentrations of P1 typical of oligotrophic conditions. PstS expression could be specifically detected by use of standard Western blotting (immunoblotting) techniques in natural mesocosm samples under conditions in which the N/P ratio was artificially manipulated to force P depletion. In addition, we have developed an immunofluorescence assay that can detect PstS expression in single Synechococcus cells both in laboratory cultures and natural samples. We show that antibodies raised against PstS cross-react with P-depleted Prochlorococcus cells, extending the use of these antibodies to both major groups of prokaryotic photosynthetic picoplankton. Furthermore, DNA sequencing of a Prochlorococcus pstS homolog demonstrated high amino acid sequence identity (77%) with the marine Synechococcus sp. strain WH7803 protein, including those residues in Escherichia coli PstS known to be directly involved in phosphate binding.


Assuntos
Proteínas de Escherichia coli , Proteínas Periplásmicas de Ligação , Fosfatos/metabolismo , Fitoplâncton/metabolismo , Proteínas de Transporte/biossíntese , Proteínas de Transporte/genética , Proteínas de Transporte/imunologia , Reações Cruzadas , Cianobactérias/genética , Cianobactérias/imunologia , Cianobactérias/metabolismo , Imunofluorescência , Expressão Gênica , Proteínas de Membrana/biossíntese , Proteínas de Membrana/genética , Proteínas de Membrana/imunologia , Dados de Sequência Molecular , Proteínas de Ligação a Fosfato , Fotossíntese , Fitoplâncton/genética , Fitoplâncton/imunologia , Microbiologia da Água
8.
Proc AMIA Annu Fall Symp ; : 799-803, 1997.
Artigo em Inglês | MEDLINE | ID: mdl-9357735

RESUMO

A new method has been developed for the Department of Orthopaedics of Vanderbilt University Medical Center to access departmental clinical data. Previously this data was stored only in the medical center's mainframe DB2 database, it is now additionally stored in a departmental SQL database. Access to this data is available via any ODBC compliant front-end or a web client. With a small budget and no full time staff, we were able to give our department on-line access to many years worth of patient data that was previously inaccessible.


Assuntos
Redes de Comunicação de Computadores , Bases de Dados como Assunto , Armazenamento e Recuperação da Informação , Interface Usuário-Computador , Sistemas Computacionais , Bases de Dados como Assunto/organização & administração , Departamentos Hospitalares , Métodos , Ortopedia , Software
9.
Comput Biol Med ; 27(1): 31-47, 1997 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-9055044

RESUMO

The broad objective was to develop an information system which integrates various sources of clinical data and facilities outcome assessment for patients evaluated in a lumbar spine service. During a patient encounter, the physician formulates a hypothesis regarding appropriate forms of treatment and he or she may then use this system to explore previous treatment outcomes for similar cases. The availability of a clinical tool that presents information in an outcome-oriented format may be highly relevant to the delivery of cost-efficient, high-quality health care and also create a formal mechanism for detecting practice variability.


Assuntos
Administração de Caso/organização & administração , Sistemas de Informação em Laboratório Clínico , Avaliação de Processos e Resultados em Cuidados de Saúde/organização & administração , Doenças da Coluna Vertebral/diagnóstico , Doenças da Coluna Vertebral/terapia , Dor nas Costas/etiologia , Demografia , Humanos , Sistemas de Informação , Vértebras Lombares , Ortopedia/estatística & dados numéricos , Software
10.
FEMS Microbiol Lett ; 142(1): 105-9, 1996 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-8759795

RESUMO

An oligomer probe was designed to detect the presence of a putative phoB gene in the genome of the marine, phycoerythrin-containing cyanobacterium Synechococcus sp. WH7803. A 2.2 kb PstI fragment, identified using this probe, was cloned and the complete nucleotide sequence determined. The fragment contained two open reading frames encoding polypeptides which display all the sequence features expected of the response regulator and histidine protein kinase elements of a two component sensory system. Northern analysis confirmed that transcription of these genes was induced by phosphate limitation. On the basis of the sequence similarities and the regulation of their transcription by the availability of inorganic phosphate (Pi) these open reading frames were designated as phoB and phoR, respectively.


Assuntos
Cianobactérias/genética , Cianobactérias/metabolismo , Genes Bacterianos , Fosfatos/metabolismo , Sequência de Aminoácidos , Proteínas de Bactérias/genética , Sequência de Bases , Clonagem Molecular , DNA Bacteriano/genética , Dados de Sequência Molecular , Fases de Leitura Aberta
11.
FEMS Microbiol Lett ; 138(2-3): 161-5, 1996 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-9026442

RESUMO

Three constitutive forms of superoxide dismutase activity have been demonstrated in the cyanobacterial marine picoplankter Synechococcus sp. WH 7803 using polyacrylamide gel activity staining techniques. A protein which gave a positive non-haem iron stain on native polyacrylamide gels exhibited N-terminal similarity to both the iron superoxide dismutase and the manganese superoxide dismutase of Escherichia coli. The metal prosthetic group of each of the three activity bands was characterised by analysing their differential sensitivities to 5 mM H2O2, 2 mM cyanide and 2 mM of the copper chelator diethyldithiocarbamate. Three distinct superoxide dismutase activities were observed, an iron superoxide dismutase, a copper/zinc superoxide dismutase and a third form which has not been identified. Growth of Synechococcus cells in ASW medium containing no added iron resulted in no alteration in the activity of the iron superoxide dismutase. Growth of cultures in the absence of copper or zinc resulted in differential changes in the activities of the copper/zinc superoxide dismutase and the unidentified superoxide dismutase.


Assuntos
Cianobactérias/enzimologia , Superóxido Dismutase/isolamento & purificação , Sequência de Aminoácidos , Meios de Cultura , Cianobactérias/genética , Cianobactérias/crescimento & desenvolvimento , Eletroforese em Gel de Poliacrilamida , Escherichia coli/enzimologia , Escherichia coli/genética , Dados de Sequência Molecular , Especificidade da Espécie , Superóxido Dismutase/genética , Superóxido Dismutase/metabolismo
12.
FEMS Microbiol Lett ; 133(1-2): 187-93, 1995 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-8566707

RESUMO

The region of the genome encoding the glucose-6-phosphate dehydrogenase gene zwf was analysed in a unicellular cyanobacterium, Synechococcus sp. PCC 7942, and a filamentous, heterocystous cyanobacterium, Anabaena sp. PCC 7120. Comparison of cyanobacterial zwf sequences revealed the presence of two absolutely conserved cysteine residues which may be implicated in the light/dark control of enzyme activity. The presence in both strains of a gene fbp, encoding fructose-1,6-bisphosphatase, upstream from zwf strongly suggests that the oxidative pentose phosphate pathway in these organisms may function to completely oxidize glucose 6-phosphate to CO2. The amino acid sequence of fructose-1,6-bisphosphatase does not support the idea of its light activation by a thiol/disulfide exchange mechanism. In the case of Anabaena sp. PCC 7120, the tal gene, encoding transaldolase, lies between zwf and fbp.


Assuntos
Anabaena/genética , Cianobactérias/genética , Sequência de Aminoácidos , Anabaena/enzimologia , Cianobactérias/enzimologia , Frutose-Bifosfatase/genética , Regulação Bacteriana da Expressão Gênica/genética , Genes Bacterianos/genética , Glucosefosfato Desidrogenase/genética , Dados de Sequência Molecular , Análise de Sequência de DNA , Homologia de Sequência de Aminoácidos
13.
J Bacteriol ; 177(12): 3527-33, 1995 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-7768863

RESUMO

Glutamine synthetase (GS) inactivation was observed in crude cell extracts and in the high-speed supernatant fraction from the cyanobacterium Synechocystis sp. strain PCC 6803 following the addition of ammonium ions, glutamine, or glutamate. Dialysis of the high-speed supernatant resulted in loss of inactivation activity, but this could be restored by the addition of NADH, NADPH, or NADP+ and, to a lesser extent, NAD+, suggesting that inactivation of GS involved ADP-ribosylation. This form of modification was confirmed both by labelling experiments using [32P]NAD+ and by chemical analysis of the hydrolyzed enzyme. Three different forms of GS, exhibiting no activity, biosynthetic activity only, or transferase activity only, could be resolved by chromatography, and the differences in activity were correlated with the extent of the modification. Both biosynthetic and transferase activities were restored to the completely inactive form of GS by treatment with phosphodiesterase.


Assuntos
Adenosina Difosfato Ribose/metabolismo , Cianobactérias/enzimologia , Glutamato-Amônia Ligase/metabolismo , Cloreto de Amônio/farmacologia , Cromatografia por Troca Iônica , Ativação Enzimática , Glutamato-Amônia Ligase/antagonistas & inibidores , Ácido Glutâmico/farmacologia , Glutamina/farmacologia , Especificidade da Espécie
14.
J Bacteriol ; 177(9): 2550-3, 1995 May.
Artigo em Inglês | MEDLINE | ID: mdl-7730289

RESUMO

A mutant of the cyanobacterium Synechococcus sp. strain PCC 7942 carrying a disrupted gene encoding glucose-6-phosphate dehydrogenase (zwf) produced no detectable glucose-6-phosphate dehydrogenase as assessed by enzyme assay and Western blot (immunoblot) analysis. This mutant exhibited significantly impaired dark viability.


Assuntos
Cianobactérias/metabolismo , Glucosefosfato Desidrogenase/metabolismo , Cianobactérias/enzimologia , Cianobactérias/genética , Cianobactérias/crescimento & desenvolvimento , Escuridão , Metabolismo Energético , Glucosefosfato Desidrogenase/genética , Luz , Mutagênese Insercional , Via de Pentose Fosfato , Fenótipo
17.
Plant Mol Biol ; 24(4): 679-83, 1994 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-7512390

RESUMO

The nucleotide sequences of the class I phycoerythrin (PE) alpha- and beta-subunit genes (cpeA and cpeB) from the marine cyanobacterium Synechococcus sp. WH7803 are reported. The cpeB gene is located upstream of cpeA with a separation of 56 nucleotides and the two genes are co-transcribed as a transcript of 1.3 kb, with the transcription startpoint being localized to 110-111 bp upstream of cpeB. The sequence of the promoter region bears no similarity to promoters reported for other cyanobacterial PE genes. Pentanucleotide repeats found upstream of some PE operons, particularly in the case of cyanobacterial strains capable of chromatic adaption, are not found in Synechococcus sp. WH7803; instead the sequence 5'-CGGTT-3' is repeated three times in the promoter region.


Assuntos
Proteínas de Bactérias/genética , Cianobactérias/genética , Genes Bacterianos/genética , Ficoeritrina/genética , Sequência de Aminoácidos , Sequência de Bases , Clonagem Molecular , Cianobactérias/química , Dados de Sequência Molecular , Óperon/genética , Ficoeritrina/química , Regiões Promotoras Genéticas/genética , RNA Bacteriano/análise , Sequências Repetitivas de Ácido Nucleico/genética , Alinhamento de Sequência , Análise de Sequência de DNA , Transcrição Gênica
18.
Appl Environ Microbiol ; 59(11): 3736-43, 1993 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-16349088

RESUMO

Five marine cyanophages propagated on Synechococcus sp. strain WH7803 were isolated from three different oceanographic provinces during the months of August and September 1992: coastal water from the Sargasso Sea, Bermuda; Woods Hole harbor, Woods Hole, Mass.; and coastal water from the English Channel, off Plymouth Sound, United Kingdom. The five cyanophage isolates were found to belong to two families, Myoviridae and Styloviridae, on the basis of their morphology observed in the transmission electron microscope. DNA purified from each of the cyanophage isolates was restricted with a selection of restriction endonucleases, and three distinguishably different patterns were observed. DNA isolated from Myoviridae isolates from Bermuda and the English Channel had highly related restriction patterns, as did DNA isolated from Styloviridae isolates from Bermuda and the English Channel. DNA isolated from the Myoviridae isolate from Woods Hole had a unique restriction pattern. The genome size for each of the Myoviridae isolates was ca. 80 to 85 kb, and it was ca. 90 to 100 kb for each of the Styloviridae isolates. Southern blotting analysis revealed that there was a limited degree of homology among all cyanophage DNAs probed, but clear differences were observed between cyanophage DNA from the Myoviridae and that from the Styloviridae isolates. Polypeptide analysis revealed a clear difference between Myoviridae and Styloviridae polypeptide profiles, although the major, presumably structural, protein in each case was ca. 53 to 54 kDa.

19.
Mol Microbiol ; 10(1): 181-91, 1993 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-7968514

RESUMO

During phosphate-limited growth the marine phycoerythrin-containing picoplanktonic cyanobacterium Synechococcus sp. WH7803 synthesizes novel polypeptides, including two abundant species of 100 kDa and 32 kDa. The 32 kDa polypeptide was localized to the cell wall, although in a related strain, Synechococcus sp. WH8103, it could be detected in both the cell wall fraction and the periplasm. The gene (designated pstS) encoding this polypeptide was cloned and shown to be present in a single copy. The deduced amino acid sequence indicated a polypeptide consisting of 326 amino acids with a calculated M(r) of 33,763. Comparison of this sequence with that obtained by microsequencing the N-terminus of the 32 kDa polypeptide showed that the mature protein was synthesized as a precursor, the first 24 amino acid residues being cleaved between two alanine residues at positions 24 and 25. The amino acid sequence of the mature polypeptide showed 35% identity and 52% similarity to the periplasmic phosphate-binding protein (PstS) from Escherichia coli, including three regions of much stronger homology which, by comparison with E. coli PstS, are directly involved in phosphate binding. Northern blot analysis revealed a pstS transcript of 1.2 kb in RNA extracted from cells grown in Pi-replete conditions and one of 1.4 kb in considerably increased abundance under Pi-depleted conditions. Homologues of the pstS gene were detected in other marine phycoerythrin-containing Synechococcus strains, but not in freshwater or halotolerant species.


Assuntos
Proteínas de Transporte/biossíntese , Cianobactérias/metabolismo , Proteínas de Escherichia coli , Escherichia coli/genética , Regulação Bacteriana da Expressão Gênica/efeitos dos fármacos , Proteínas de Membrana/biossíntese , Proteínas Periplásmicas de Ligação , Fosfatos/farmacologia , Sequência de Aminoácidos , Sequência de Bases , Transporte Biológico/genética , Proteínas de Transporte/genética , Parede Celular/metabolismo , Cianobactérias/química , Cianobactérias/classificação , Cianobactérias/genética , Proteínas de Membrana/genética , Dados de Sequência Molecular , Proteínas de Ligação a Fosfato , Fosfatos/metabolismo , Ficoeritrina/análise , Alinhamento de Sequência , Homologia de Sequência de Aminoácidos , Especificidade da Espécie
20.
Curr Biol ; 3(5): 265-73, 1993 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-15335746

RESUMO

BACKGROUND: The chaperonins, a family of molecular chaperones, are large oligomeric proteins that bind nonnative intermediates of protein folding. They couple the release and correct folding of their ligands to the binding and hydrolysis of ATP. Chaperonin 60 (cpn60) is a decatetramer (14-mer) of 60 kD subunits. Folding of some ligands also requires the cooperation of cpn10, a heptamer of 10 kD subunits. RESULTS: We have determined the three-dimensional arrangements of subunits in Rhodobacter sphaeroides cpn60 in the nucleotide-free and ATP-bound forms. Negative stain electron microscopy and tilt reconstruction show the cylindrical structure of the decatetramer comprising two rings of seven subunits. The decatetramer consists of two cages joined base-to-base without a continuous central channel. These cages appear to contain bound polypeptide with an asymmetric distribution between the two rings. The two major domains of each subunit are connected on the exterior of the cylinder by a narrower bridge of density that could be a hinge region. Binding of ATP to cpn60 causes a major rearrangement of the protein density, which is reversed upon the hydrolysis of the ATP. Cpn10 binds to only one end of the cpn60 structure and is visible as an additional layer of density forming a cap on one end of the cpn60 cylinder. CONCLUSIONS: The observed rearrangement is consistent with an inward 5-10 degrees rotation of subunits, pivoting about the subunit contacts between the two heptamers, and thus bringing cpn60 domains towards the position occupied by the bound polypeptide. This change could explain the stimulation of ATPase activity by ligands, and the effects of ATP on lowering the affinity of cpn60 for ligands and on triggering the release of folding polypeptides.

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