Role(s) of Acetylation in human pathogen Helicobacter pylori

Abstract

Helicobacter pyloris (H.pylori) a Gram‐negative bacterium whose infection of the human stomach triggers a chronic gastritis that can evolve into a series of severe pathologies such as gastroduodenal ulcers and cancer. H.pylori infects more than 50% of world population. Its amazing diversity and variability are major contributors to this success by allowing the emegence of new alleles. The bacterium lacks SOS response, DNA mismatch repair system, has a huge repertoire of restriction‐modification systems and is highly competent. These characteristics compelled us to investigate its all‐possible regulatory system (s). Acetylation‐a post‐translational modification has been proven to be a major regulatory machinery in prokaryotic physiology Acetylome analysis of different strains of H. pylori showed the presence of prominent and strain specific protein acetylation. Mass‐spectrometry based analysis showed that acetylated proteins participate in diverse biological processes such as metabolic pathways, transcription, translation, cell signalling and motility. In addition, acetylome analysis showed that two Cag pathogenicity island proteins. Cag 7, Cag 14, UvrD helicase involved in nucleotide excision repair, DNA methyltransferase‐ HPyAVIA, and DprA‐ involved in Natural Transformation process were acetylated. HP0935, a putative N‐acetyltransferase belonging to the GNAT superfamily was identified as possible protein acetyltransferase. It was observed that HP0935 acetylates L‐amino acids such as arginine and methionine at Nα amino group and lysine at both Nα and Nε amino group. Mutational and pH analysis of HP0935 suggest that a possible catalytic mechanism involves deprotonation of amino group of substrates by conserved water molecule followed by nucleophilic attack of deprotonated amino group on Ac‐CoA. Furthermore, Tyr127 act as a general acid that protonates the leaving thiolate anion of Coenzyme A. It was observed that ATPase and helicase activity of HPUvrD was regulated by both enzymatic (HP0935) and non‐enzymatic (Ac‐CoA) acetylation while the methyltransferase activity of M. HPyAVIA was enhanced only by enzymatic (HP0935) acetylation. These observations suggest acetylation of several key proteins plays a role in pathogenesis and in Natural transformation of H. pylori.