PROTEIN HPN - CLONING AND CHARACTERIZATION OF A HISTIDINE-RICH METAL-BINDING POLYPEPTIDE IN HELICOBACTER-PYLORI AND HELICOBACTER-MUSTELAE

Helicobacter pylori is a human gastrointestinal pathogen involved in g astritis, duodenal ulcers, and gastric neoplasia, This microorganism p roduces large amounts of a urease which, like all known ureases, has n ickel in the active site. We have identified a protein in clinical iso lates of H. pylori and an identical protein in the ferret pathogen Hel icobacter mustelae that strongly binds Ni2+ and Zn2+, This protein has been named Hpn to emphasize its origins in H. pylori and its affinity for nickel. The encoding hpn gene, cloned and expressed in Escherichi a coli ER1793, has an open reading frame (180 bp) that specifies a pro tein with a calculated molecular mass of 7,077 Da and with the same am ino-terminal sequence as that of wild-type Hpn, The deduced sequence o f Hpn consists of 60 amino acids, of which 28 (47%) are histidines. Th e hpn gene does not map with the urease gene cluster on the H. pylori chromosome. An Hpn-negative, isogenic H. pylori strain, generated by h pn gene deletion and grown on blood agar, had the same urease activity that wild-type cells did. Thus, the role of Hpn in helicobacters is u nknown.