Assuntos
Doenças dos Peixes/microbiologia , Infecções Estreptocócicas/veterinária , Streptococcus agalactiae/isolamento & purificação , Tilápia , Animais , Aquicultura , Gana , Tipagem de Sequências Multilocus/veterinária , Infecções Estreptocócicas/mortalidade , Streptococcus agalactiae/classificação , Streptococcus agalactiae/genéticaRESUMO
The Salmonella typhimurium protein SlyA(ST), originally described as a cytolysin, shows sequence similarities to several known bacterial regulatory proteins. A homologue to the Slya(ST) gene has been localised to min 37 of the Escherichia coil K-12 chromosome and has been designated SlyA(EC). When introduced in trans on a plasmid, the SlyA(EC) gene conferred a haemolytic phenotype on wild-type but not clyA-knockout strains of E. coli K-12. The clyA gene encodes a novel haemolysin that is not expressed by wild-type E. coli under tested laboratory conditions. Western and Northern blot analyses, and DNA-band-shift assays support a model whereby the SlyA(EC) protein activates clyA expression by binding to the clyA promoter region, thereby supporting the sequence similarity data in suggesting that SlyA(ST) is a haemolysin activator rather than being a haemolysin per se.
Assuntos
Proteínas de Bactérias , Toxinas Bacterianas/genética , Escherichia coli/genética , Regulação Bacteriana da Expressão Gênica , Proteínas Hemolisinas/genética , Hemólise , Fatores de Transcrição , Sequência de Aminoácidos , Toxinas Bacterianas/metabolismo , Sequência de Bases , Clonagem Molecular , Escherichia coli/metabolismo , Escherichia coli/patogenicidade , Proteínas Hemolisinas/biossíntese , Proteínas Hemolisinas/metabolismo , Dados de Sequência Molecular , Regiões Promotoras GenéticasRESUMO
Transcript mapping and studies with lacZ translational fusions have shown that the pdhR gene (formerly genA) is the proximal gene of the pdhR-aceE-aceF-lpd operon encoding the pyruvate dehydrogenase (PDH) complex of Escherichia coli. A pdhR-lpd read-through transcript (7.4 kb) initiating at the pyruvate-inducible pdh promoter, and a smaller lpd transcript (1.7 kb) initiating at the independent lpd promoter, were identified. Evidence showing that the pdhR gene product negatively regulates the synthesis of the PdhR protein and the PDH complex via the pdh promoter was obtained, with pyruvate (or a derivative) serving as the putative inducing coeffector. The partially purified PdhR protein was also found to specifically retard and protect DNA fragments containing the pdh promoter region. The pdh promoter was not strongly controlled by ArcA, FNR or CRP.
Assuntos
Acetiltransferases/genética , Proteínas de Bactérias/genética , Di-Hidrolipoamida Desidrogenase/genética , Proteínas de Escherichia coli , Escherichia coli/genética , Genes Bacterianos , Complexo Cetoglutarato Desidrogenase/genética , Óperon , Complexo Piruvato Desidrogenase/genética , Fatores de Transcrição/genética , Acetiltransferases/biossíntese , Sequência de Aminoácidos , Proteínas de Bactérias/metabolismo , Sequência de Bases , DNA Bacteriano/genética , DNA Bacteriano/metabolismo , Di-Hidrolipoamida Desidrogenase/biossíntese , Di-Hidrolipoil-Lisina-Resíduo Acetiltransferase , Indução Enzimática , Escherichia coli/enzimologia , Regulação Bacteriana da Expressão Gênica , Complexo Cetoglutarato Desidrogenase/biossíntese , Dados de Sequência Molecular , Regiões Promotoras Genéticas , Complexo Piruvato Desidrogenase/biossíntese , Proteínas Recombinantes de Fusão/biossíntese , Sequências Reguladoras de Ácido Nucleico , Proteínas Repressoras/genética , Fatores de Transcrição/metabolismo , Transcrição GênicaRESUMO
The aceE-aceF-lpd genes encoding the pyruvate dehydrogenase (PDH) complex of Escherichia coli are preceded by a gene encoding a putative transcriptional regulator, PdhR (formerly designated GenA). Enzymological tests and studies with pdhR-lacZ and aceE-lacZ translational fusions have shown that a constitutive mutation (acec816), which increases PDH complex synthesis to the pyruvate-induced level in the absence of inducer, is recessive to the wild-type pdhR gene in trans. Sequence comparisons further showed that the acec816 mutation affects a single site in the pdhR gene leading to an Arg118 (CGU)-->Cys (UGU) substitution in the PdhR protein. The results support the view that synthesis of the PDH complex is regulated from the pdhR promoter of a pdhR-aceEF-lpd operon.
Assuntos
Proteínas de Bactérias/genética , Proteínas de Escherichia coli , Escherichia coli/enzimologia , Genes Reguladores , Mutação , Complexo Piruvato Desidrogenase/biossíntese , Proteínas Repressoras , Fatores de Transcrição/genética , Sequência de Aminoácidos , Proteínas de Bactérias/metabolismo , Sequência de Bases , Clonagem Molecular , DNA Bacteriano , Escherichia coli/genética , Regulação Bacteriana da Expressão Gênica , Dados de Sequência Molecular , Plasmídeos , Biossíntese de Proteínas , Complexo Piruvato Desidrogenase/genética , Fatores de Transcrição/metabolismoRESUMO
A new family of bacterial regulatory proteins has been identified by sequence similarity. The family contains the repressor of the Bacillus subtilis gluconate operon (GntR), the regulators for histidine utilization in Pseudomonas putida (HutCPp) and Klebsiella aerogenes (HutCKa), the repressor (FadR) of fatty acid degradation in Escherichia coli, a regulator involved in the conjugal transfer of the broad host range plasmid pIJ101 (KorA), and three proteins of unidentified function in E. coli (GenA, P30 and PhnF). The proteins share amino acid sequence similarities in a 69-residue N-terminal region. A helix-turn-helix motif is predicted in the most highly-conserved segment of each protein suggesting that they are members of a new family of helix-turn-helix DNA-binding proteins.
