Characterization of an Acidic-pH-Inducible Stress Protein (hsp70), a Putative Sulfatide Binding Adhesin, fromHelicobacter pylori
ABSTRACT The in vitro glycolipid binding specificity of the gastric pathogenHelicobacter pylori is altered to include sulfated glycolipids (sulfatides) following brief exposure of the organism to acid pH typical of the stomach. This change is prevented by anti-hsp70 antibodies, suggesting that hsp70 may be a stress-induced surface adhesin, mediating sulfatide recognition. To facilitate investigation of the role of hsp70 in attachment, we have cloned and sequenced theH. pylori hsp70 gene (dnaK). Thehsp70 gene was identified by probing a cosmid DNA library made from H. pylori 439 with a PCR amplicon generated with oligonucleotides synthesized to highly conserved regions ofdnaK. The 1.9-kb H. pylori hsp70 gene encodes a product of 616 amino acids. Primer extension analysis revealed a single transcription start site, while Northern blot analysis established that hsp70 was preferentially induced by low pH rather than by heat shock. The ability ofH. pylori to alter its glycolipid binding specificity following exposure to low pH by upregulating hsp70 and by expressing hsp70 on the bacterial surface may provide a survival advantage during periods of high acid stress.