RESUMO
The assT gene encodes an arylsulfate sulfotransferase, an enzyme that catalyzes sulfuryl transfer from phenolic sulfate to a phenolic acceptor. In Salmonella enterica serovar Typhi IMSS-1, the assT gene is located upstream of the dsbL and dsbI genes, which are involved in a disulfide bond formation required for its activation. The assT-dsbL-dsbI gene cluster forms an operon transcribed by a LeuO-dependent promoter, in rich medium A (MA). Interestingly, in the absence of cloned leuO and in a ΔleuO background, two transcription start sites were detected for assT and two for dsbL-dsbI in minimal medium. The H-NS nucleoid protein repressed the expression of the assT-dsbL-dsbI LeuO-dependent operon, as well as of the assT transcriptional units. Thus, the expression of the assT-dsbL-dsbI gene cluster depends on the global regulatory proteins LeuO and H-NS, as well as on specific growth conditions.
Assuntos
Proteínas de Bactérias/metabolismo , Regulação Bacteriana da Expressão Gênica/fisiologia , Oxirredutases/metabolismo , Salmonella typhi/metabolismo , Fatores de Transcrição/metabolismo , Proteínas de Bactérias/genética , DNA Bacteriano/genética , Genoma Bacteriano , Família Multigênica , Mutação , Óperon , Oxirredutases/genética , Regiões Promotoras Genéticas , RNA Bacteriano/genética , Salmonella typhi/genética , Fatores de Transcrição/genética , Transcrição GênicaRESUMO
LeuO is a LysR-type transcriptional regulator that has been implicated in the bacterial stringent response and in the virulence of Salmonella. A genomic analysis with Salmonella enterica serovar Typhi revealed that LeuO is a positive regulator of OmpS1, OmpS2, AssT, and STY3070. In contrast, LeuO down-regulated the expression of OmpX, Tpx, and STY1978. Transcriptional fusions supported the positive and negative LeuO regulation. Expression of ompS1, assT, and STY3070 was induced in an hns mutant, consistent with the notion that H-NS represses these genes; transcriptional activity was lower for tpx and STY1978 in an hns background, suggesting that this global regulatory protein has a positive effect. In contrast, ompS2 and ompX expression appeared to be H-NS independent. LeuO specifically bound to the 5' intergenic regions of ompS2, assT, STY3070, ompX, and tpx, while it was not observed to bind to the promoter region of STY1978, suggesting that LeuO regulates in direct and indirect ways. In this work, a novel set of genes belonging to the LeuO regulon are described; interestingly, these genes are involved in a variety of biological processes, suggesting that LeuO is a global regulator in Salmonella.
Assuntos
Proteínas da Membrana Bacteriana Externa/genética , Regulação Bacteriana da Expressão Gênica , Salmonella typhi/genética , Transativadores/genética , Proteínas da Membrana Bacteriana Externa/metabolismo , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Cloranfenicol O-Acetiltransferase/metabolismo , Biologia Computacional , Pegada de DNA , Desoxirribonuclease I/metabolismo , Eletroforese em Gel Bidimensional , Porinas , Regiões Promotoras Genéticas , Regulon , Salmonella typhi/metabolismo , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz , Sítio de Iniciação de TranscriçãoRESUMO
We have isolated a novel outer membrane protein (OMP)-encoding gene from Salmonella typhi (St), termed ompS1, using the ompF gene of Escherichia coli (Ec) as a heterologous probe. The structural ompS1 gene codes for an OmpS1 polypeptide that consists of 373 amino acids (aa) in the mature product, with a putative 21-aa leader sequence, containing highly conserved aa residues that have been implicated in pore formation. Mature OmpS1 (41 kDa) is larger than the OmpC, OmpF and PhoE St and Ec porins. In contrast to the major porins, it is undetectable in Coomassie-stained OMP preparations; although, when ompS1 was cloned into a high-copy-number plasmid under the control of the inducible tac promoter, it was detectable along with major OMPs. The 5' regulatory region of ompS1 has five putative binding sites for OmpR, a positive transcriptional regulator. The ompS1 gene shows restriction-fragment length polymorphism (RFLP) among Salmonellae.
Assuntos
Proteínas da Membrana Bacteriana Externa/genética , Salmonella typhi/genética , Sequência de Aminoácidos , Sequência de Bases , DNA Bacteriano/genética , Dados de Sequência Molecular , Hibridização de Ácido Nucleico , Porinas , Sequências Reguladoras de Ácido Nucleico , Homologia de Sequência de AminoácidosRESUMO
While probing the vicinity of ompC, a copy of the IS200 insertion element was found between the gyrA and rcsC genes of Salmonella typhi, the causal agent of typhoid fever. This distinctive feature was conserved throughout 63 S. typhi isolates of different geographical origins and was absent from 46 other Salmonella serotypes, including those most associated with human infections, as well as from 19 other enteric bacteria. Furthermore, the location of this IS200 copy corresponds to a constant band, present throughout the 14 PstI S. typhi IS200 fingerprints, encompassing several Vi phage types. Interestingly, an apparently unrelated serotype not frequently associated with human disease, Salmonella weltevreden, contained an IS200 copy at the same position, although it was accompanied by an additional segment of cryptic DNA. On the basis of these findings, PCR assays were designed for molecular typing of S. typhi, and these are potentially useful in studying the epidemiology of typhoid fever.