Global control of Campylobacter jejuni biology by protein lysine acetylation.

The small genome size and regulator complement of C. jejuni suggests post-transcriptional adaptation mechanisms might be crucial in its life-cycle, but the control of protein activity by post-translational modifications (PTMs) of specific amino acids has not been widely studied. Here, we show for the first time that protein lysine acetylation is widespread in C. jejuni and that it impacts multiple aspects of its biology. Immunoblots using a commercially available anti-AcK antibody detected a wide range of acetylated proteins in strain NCTC 11168. While the acetylation profile was similar in both wild-type and pta mutants, deletion of ackA clearly increased protein acetylation, which returned to wild-type levels in a complemented strain. This pattern strongly suggests (i) a dominant role for chemical acetylation from acetyl-P, (ii) acetyl-CoA dependent acetylation via acetyl-transferases in the pta mutant. We identified a Sirtuin homologue, CobB which we show is a lysine deacetylase. Using a state-of-the-art proteomic workflow with antibody enrichment coupled to LC-MS/MS analysis, we have identified 7,322 acetylation sites in over 1,200 proteins in wild-type cells. Therefore, over 70% of the C. jejuni proteome is acetylated, a greater proportion than in any other bacterium to date. The cobB mutation caused significant alterations in the C. jejuni acetylome; we identified 566 lysines that are controlled by CobB and show that many fundamental cellular processes in C. jejuni are impacted by this reversible acetylation, including chemotaxis, motility, nitrogen and carbon metabolism. Target candidate proteins with CobB sensitive lysines were selected for further characterisation, to determine the effects of acetylation on their activity. Our results have revealed a previously unsuspected but extensive landscape of protein regulation by acetylation in C. jejuni.