ヘリコバクター・ピロリ菌の胃酸耐性としてのウレアーゼ・オペロンの転写調節および同菌の胃定着機序

概要

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Helicobacter pylori is known to colonize in the human stomach by neutralizing acidic condition with urease activity. The effect of acid on the transcription of the urease operon was investigated to determine whether H. Pylori is has a novel mechanism under such conditions. We investigated the transcription of the urease gene cluster ureABIEFGH in Helicobacter pylori to determine the regulation of gene expression of the highly produced enzyme urease. Northern blot hybridization analysis demonstrated that cells of the wild-type strain grown in an ordinary broth had transcripts of ureAB, ureABI, ureI, ureIE' and ure'FGH, but cells of a ureIdisrupted mutant had only the ureAB transcript. When the wild-type cells were exposed to pH 8 for 30 min, very little mRNA was detected. However, when exposed to pH 6, a large amount of the ureIE ”transcript, which was longer than the ureIE' transcript, together with the additional transcripts ureABIEFGH and ure' EFGH were detected. Rifampicin addition experiments demonstrated that urease mRNAs, and the ureIE' transcripts in particular, are more stable at pH 5.5 than at pH 7. In accord with these results, urease activity in the crude cell extract of the pH 5.5 culture was twice as much as that of the pH 7 culture, although the amounts of UreA and UreB detected by immunoblot analysis were similar. …
2001-04-30