HELICOBACTER-PYLORI EXTRACTS EXHIBIT NICOTINAMIDE ADENINE DINUCLEOTIDE-DERIVED ADENYLATION BUT NOT MONO(ADENOSINE 5'-DIPHOSPHATE-RIBOSYL)ATION OF DNA-LIGASE

The issue of toxins produced by Helicobacter pylori (H. pylori) urgent ly requires clarification given that the bacterium causes gastric epit helial cell damage which may lead to precancerous and cancerous change s. During an investigation of the possibility of mono(adenosine 5'-dip hosphate (ADP)-ribosyl)ation by H. pylori products, as observed for ot her bacterial toxins, we found that radioactivity of [adenylate-P-32]n icotinamide adenine dinucleotide (NAD) is incorporated into an H. pylo ri protein of 80 kDa after incubation with crude bacterial extract. In contrast, [carbonyl-C-14]NAD did not show any radioactivity incorpora tion. Unexpectedly, treatment of the modified protein with 0.1 N HCl, but not 0.1 N NaOH, released the AMP moiety. Such chemical properties are characteristic of bacterial DNA ligase-AMP complexes. We found tha t an antibody raised against Escherichia coli DNA ligase CEC 6.5.1.2] immunoprecipitated the modified 80 kDa protein. Our results indicate t hat incorporation of radioactivity derived from NAD into the 80 kDa pr otein was due to adenylation, but not mono(ADP-ribosyl)ation, of the D NA ligase of H. pylori.