PURIFICATION OF HELICOBACTER-PYLORI SUPEROXIDE-DISMUTASE AND CLONING AND SEQUENCING OF THE GENE

The superoxide dismutase (SOD) of Helicobacter pylori, a pathogenic ba cterium which colonizes the gastric mucosa, evoking a marked inflammat ory response, was purified and characterized, and the N-terminal amino acid sequence was determined. The enzyme consists of two identical su bunits each with an apparent molecular weight of 24,000. Analysis of t he primary structure and inhibition studies revealed that H. pylori po ssesses a typical procaryotic iron-containing enzyme. No other isoenzy mes could be detected. Indirect gold immunostaining of R. pylori SOD w ith a polyclonal antibody directed against the iron-containing SOD of Escherichia coli showed a surface-associated localization of the enzym e. The H. pylori SOD gene was cloned by functional complementation of a SOD-deficient E. coil mutant. Sequencing and alignment revealed stri king homology to the following facultative intracellular human pathoge ns: Listeria ivanovii, Listeria monocytogenes, Coxiella burnetti, Porp hyromonas gingivalis, Legionella pneumophila, and Entamoeba histolytic a. An open reading frame of 642 bp encoding 214 amino acids was determ ined. There was no leader sequence detectable. Cloning of the H. pylor i SOD gene is one of the prerequisites to investigation of its pathoph ysiological role in the defense against antimicrobial mechanisms of po lymorphonuclear granulocytes.