Metal dependency of HP0892 toxin from Helicobacter pylori HP0892-HP0893 Toxin-Antitoxin system

Abstract

Helicobacter pylori are helix-shaped, gram-negative, microaerophilic bacteria. It can survive in the extreme acidic environment, colonize to the stomach's epithelial cell layer. It is a major cause of gastroduodenal diseases, such as gastritis, peptic ulcer disease and stomach cancer. 10% of children and 80% of adults infected with H. pylori are asymptomatic, but disease symptoms appear, the antibiotics are required. The first try is triple therapy ; clarithromycin, amoxicillin, PPI. But these antibiotics are caused some side effects and resistance. It is because these several drugs stimulate the gastrointestinal tract, and Helicobacter pylori have diverse resistance strain. Especially, Toxin-Antitoxin system plays an important role in resistance. HP0892 is toxin of type II toxin-antitoxin system in Helicobacter pylori. This protein has ribonuclease activity. Toxin-Antitoxin systems are found in many bacteria and it consists of the toxin containing cell toxicity and the antitoxin neutralizing toxin. This system is expressed under stressful conditions, and cell growth is inhibited by the toxin. Toxin-Antitoxin systems are related to antibiotic resistance and pathogenecity. HP0892 toxin has intrinsic ribonuclease activity so this protein is attack the mRNA. Several divalent metals affect the ribonuclease folding, substrate specificity, efficiency. We are study metal dependency of HP0892. In ribonuclease activity assay, ribonuclease activity is specifically inhibited by Cu2+ and Zn2+. Seen as a result of circular dichroism, Zn2+ stabilizes protein structure and Cu2+ destabilizes it. Due to find out Kd and binding site, we performed ITC and NMR titration.