Identification and purification of a cpn60 heat shock protein homolog from Helicobacter pylori

Abstract

Helicobacter pylori is associated with gastritis and peptic ulcer disease in humans. We have identified a homolog of the chaperonin cpn60 family of heat shock proteins in H. pylori, referred to as Hp54K. Hp54K, purified from water-extractable H. pylori proteins, migrated as a single band at 54 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Its native molecular mass was 740 kDa; thus, Hp54K apparently comprises a 14-mer. The N-terminal 33 residues of Hp54K exhibited 60.6, 57.6, 54.5, 54.5, 51.5, and 51.5% identity with corresponding sequences in the following cpn60 homologs: HtpB (Legionella pneumophila), P1 (human mitochondria), GroEL (Escherichia coli), BA60K (Brucella abortus), HypB (Chlamydia trachomatis), and the 65-kDa immunodominant protein of Mycobacterium bovis BCG, respectively. Hp54K was the only protein recognized in whole-cell preparations of H. pylori by immunoblotting using monospecific antisera against cpn60 homologs from L. pneumophila, E. coli, C. trachomatis, and M. bovis BCG. Antiserum against Hp54K recognized proteins with molecular masses of 50 to 60 kDa in a large number of gram-negative bacteria, consistent with the known highly conserved nature of cpn60 proteins. Hp54K is a major protein and is immunogenic in humans infected with H. pylori. Thus, Hp54K shares many similarities with known cpn60 homologs. On the basis of the proposed role of other cpn60 proteins in induction of chronic inflammation, immune cross-reactivity between Hp54K and gastric tissue may provide an important link between H. pylori infection and gastritis.