• Journal of Microbiology
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• v.39 no.2
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• pp.109-115
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• 2001

Salmonella typhimurium possesses a cad operon, which contributes to an adaptive response against an acidifying environment. In Escherichia coli, the activation of the cad operon is dependent on cadC, which is located upstream of the operon. However, the activator of cad operon in S. typhimurium has not been known until now. In this study, we selected a putative cadC mutant by trasposon mutagenesis and cloned the cadc of S. typhimurium. Moreover, the cadC mutant was complemented by cadC clone. The cadC gene from S. typhimurium LT-2 consists of 1539 bp encoding a polypeptide ob 512 amino acids, and shows sequence similarity to cadC of E. coli with 53% identity and 67% similarity. The hydrophobicity profile of th S. typhimurim CadC sequence is very similar to E. coli CadC.

• Korean Journal of Microbiology
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• v.37 no.4
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• pp.259-264
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• 2001

It has been well known that the expression of S. typhimurium cadBA operon requires at least two extracellular signals: low pH and high concentration of lysine. To better understand the nature of pH-dependent and lysine dependent signal transduction, mutants were isolated in JF2238(cadA-lacZ) by Tn10 insertion, spontaneous mutagenesis, and EMS treatment. Two mutants were isolated from JF2238, expressed as a cadA-lacZ operon fusion in various growth conditions, and analyzed to have mutations in cadC, a gene encoding a function necessary for transcriptional activation of cadBA. One isolate (cadC6) conferred pH-independent and lysine-independent cadBA expression and the other(cadC4) showed pH-independent and lysine-dependent cadBA expression. cadR::Tn10 and cadR4 mutants were expressed in the absence of exogenously added lysine. They were also resistant to thiosine and complemented by lysP clone from E. coli. Thus, in the absence of exogenous lysine, cadR is a negative regulator of cadBA expression. Cadaverine, the product of lysine decarboxylation, was shown to inhibit expression of cadA-lacZ fusion in cad $C^+$ cell.

• Journal of Microbiology and Biotechnology
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• v.18 no.11
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• pp.1755-1761
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• 2008

The present study revealed that Lrp, a leucine-responsive regulatory protein, is involved in the regulation of cadBA transcription through activation of $P_{cadBA}$. The influence of Lrp on $P_{cadBA}$ was mediated by CadC, and thereby, CadC was able to compensate for the lack of Lrp in the activation of $P_{cadBA}$. Western blot analyses and EMSA demonstrated that the cellular level of CadC was not significantly affected by Lrp, and that Lrp exerted its effect by directly binding to $P_{cadBA}$. These combined results suggested that CadC and Lrp function cooperatively to activate the $P_{cadBA}$ rather than sequentially in a regulatory cascade.

• Journal of Microbiology and Biotechnology
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• v.14 no.5
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• pp.1093-1098
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• 2004

An open reading frame encoding CadC, consisting of 526 amino acids, was identified from the upstream region of the Vibrio vulnificus cadBA operon. The deduced amino acid sequences of the cadC were 22 to 78% similar to those reported from other Enterobacteriaceae. Functions of cadC gene on acid tolerance were assessed by comparing acid tolerances of V. vulnificus and its isogenic mutant, whose cadC gene was inactivated by allelic exchanges. The results demonstrated that the gene product of cadC contributes to acid tolerance of V. vulnificus, and that its contribution is dependent on prior exposure of cells to moderately acidic pH. The cellular level of cadB and cadA transcripts decreased in the cadC mutant, indicating that CadC exerts its effect on acid tolerance of V. vulnificus by enhancing the expression of cadBA in a pH-dependent manner.