PROPERTIES OF THE P-TYPE ATPASES ENCODED BY THE COPAP OPERONS OF HELICOBACTER-PYLORI AND HELICOBACTER-FELIS

The cop operons of Helicobacter pylori and Helicobacter felis were clo ned by gene library screening. Both operons contain open reading frame s for a P-type ion pump (CopA) with homology to Cd2+ and Cu2+ ATPases and a putative ion binding protein (CopP), the latter representing a C opZ homolog of the copYZAB operon of Enterococcus hirae. The predicted CopA ATPases contained an N-terminal GMXCXXC ion binding motif and a membrane-associated CPC sequence. A synthetic N-terminal peptide of th e H. pylori CopA ATPase bound to Cu2+ specifically, and gene disruptio n mutagenesis of CopA resulted in an enhanced growth sensitivity of H. pylori to Cu2+ but not to other divalent cations. As determined exper imentally, H. pylori CopA contains four pairs of transmembrane segment s (H1 to H8), with the ATP binding and phosphorylation domains lying b etween H6 and H7, as found for another putative transition metal pump of H. pylori (K. Melchers, T. Weitzenegger, A. Buhmann, W. Steinhilber , G. Sachs, and K. P. Schafer, J. Biol. Chem. 271:446-457, 1996). The corresponding transmembrane segments of the H. felis CopA pump were id entified by hydrophobicity analysis and via sequence similarity. To de fine functional domains, similarly oriented regions of the two enzymes were examined for sequence identity. Regions with high degrees of ide ntity included the N-terminal Cu2+ binding domain, the regions of ATP binding and phosphorylation in the energy transduction domain, and a t ransport domain consisting of the last six transmembrane segments with conserved cysteines in H4, H6, and H7. The data suggest that H. pylor i and H. felis employ conserved mechanisms of ATPase-dependent copper resistance.