The Cysteine-rich Protein A fromHelicobacter pyloriIs a β-Lactamase

Peer R. E. Mittl, Lucas Lüthy, Peter Hunziker, Markus G. Grütter
2000 Journal of Biological Chemistry  
Among the large number of hypothetical proteins within the genomes of Helicobacter pylori, there is a family of unique and highly disulfide-bridged proteins, designated family 12, for which no function could originally be assigned. Sequence analysis revealed that members of this family possess a modular architecture of ␣/␤-units and a stringent pattern of cysteine residues. The H. pylori cysteine-rich protein A (HcpA), which is a member of this family, was expressed and refolded from inclusion
more » ... ded from inclusion bodies. Six pairs of cysteine residues, which are separated by exactly seven residues, form disulfide bridges. HcpA is a ␤-lactamase. It slowly hydrolyzes 6-aminopenicillinic acid and 7-aminocephalosporanic acid (ACA) derivatives. The turnover for 6-aminopenicillinic acid derivatives is 2-3 times greater than for ACA derivatives. The enzyme is efficiently inhibited by cloxacillin and oxacillin but not by ACA derivatives or metal chelators. We suggest that all family 12 members possess similar activities and might be involved in the synthesis of the cell wall peptidoglycan. They might also be responsible for amoxicillin resistance of certain H. pylori strains. Helicobacter pylori is a spiral-shaped, Gram-negative microorganism that was first described in 1983 by Warren and Marshall (1). It settles in the gastric lumen of primates, and it is a major risk factor for several gastric diseases (2), such as chronic active gastritis (1), gastric adenocarcinoma (3), and MALT lymphoma (4, 5). The implications of H. pylori in several gastric and cardiovascular diseases have been reviewed in several articles (6 -8). The genomes of strains 26695 and J99 have been completely sequenced (9, 10), and the open reading frames where grouped into 95 protein families. For approximately two-thirds of all ORFs, 1 a function was assigned by sequence comparisons. A group of seven ORFs that were unique to H. pylori was iden-
doi:10.1074/jbc.m001869200 pmid:10748053 fatcat:fpjeq4visrfo3prcyugonlya74