• 한국미생물·생명공학회지
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• 제28권6호
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• pp.316-321
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• 2000

Role of enterotoxin from Salmonella in pathogenesis is not know. Enterotoxin gene from Salmonella typhimurium(stn) encodes a 29kDa toxin that has no homology to any other known enterotoxins. Expression of stn is enthanced upon contact with epithelial cell but not all strains having the stn gene express Stn, Based on PCR analysis, we found that all 36 clinical strains of Salmonella isolated in Korea tested carried the stn gene. To understand the trgulation of the stn transcription, the expression of stn was studies in vitro. RNA polymerase was purified by polymin P fraction-ation, DNA-agarose affinity chromatography, and Mono-Q ion exchange chromatography from Salmonella. The expression of stn was inhibited by cAMP·CRP complex by about 50%.

• Journal of Microbiology and Biotechnology
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• 제13권4호
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• pp.598-606
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• 2003

Salmonella encodes an enterotoxin (Stn) which possesses biological activity similar to the cholera toxin. Stn contributes significantly to the overall virulence of S. typhimurium in a murine model. The production of Stn is enhanced in a high-osmolarity medium and by contact with epithelial cells. In the present study, the in vitro and in vivo transcriptional regulations of the sin promoter revealed two promoters, P1 and P2. The P1 promoter identified by a primer extension analysis of stn mRNA exhibited a switching mechanism in vivo. Depending on the growth stage, transcription was initiated from different start sites termed $P1_S\;and\;P1_E$. $P1_S$, recognized by RNA polymerase containing ${\sigma}^S(E{\sigma}^S),\;and\;P1_E$, recognized by $E{\sigma}^70$, were activated during the stationary and exponential phases, respectively, while $P1_S\;and\;P1_E$ were both negatively regulated by CRPㆍcAMP and H-NS. Results revealed that $P1_S$ was the responsible promoter activated under a high osmolarity and low pH. The P2 promoter was identified 45 nucleotides downstream from $P1_E$ and negatively controlled by CRPㆍcAMP in vitro. No P2 activity was detected in vivo. The regulation of stn expression monitored using a Pstn::egfp fusion indicated that $E{\sigma}^S$ was required for the induction of stn and various factors were involved in stn regulation inside animal cells.