pH-dependent protein profiles of Helicobacter pylori analyzed by two-dimensional gels

Background. Helicobacter pylori survives transient exposure to extreme acid prior to adherence and growth on the gastric epithelium at neutral pH. Materials and Methods. The effect of pH stress on protein profiles of H. py lori was observed using two-dimensional gel electrophoresis (2-D gels). H. pylori 26695 was grown microaerobically in tryptone-yeast extract broth, 3% fetal bovine serum. Growth in acid alkalinized the medium, whereas growth in base caused acidification. For 2-D gel analysis of protein profiles, cul tures were grown in media buffered at pH 5.7 and at pH 7.5. Results. Under all pH conditions, the most abundant proteins observed were the urease structural subunit UreB and the chaperonin GroEL. Growth in acid significantly increased the abundance of UreB. Thus, urease expression is not completely constitutive, as reported previously, but shows regulation b y pH. Another protein observed only at low pH was identified as mammalian a polipoprotein A-I, possibly taken up by H. pylori from bovine serum in the growth medium. This finding, if confirmed, suggests that uptake of high-den sity lipoprotein from the human host may facilitate acquisition of choleste rol, required for formation of the unique cholesteryl glucosides in the mem brane of H. pylori. In growth above pH 7, three stress proteins were induce d: GroES (HspA), GroEL (HspB), and the antioxidant AhpC homolog TsaA. In ad dition, N-terminal sequence analysis identified five additional proteins th at had not previously been reported on 2-D gels of H. pylori (FMN, SodB, Tr xB, TsaA, and Tsr). Conclusions. In summary, our 2-D gel study reveals expression of several pr oteins dependent on growth pH.