In Typhimurium and , Nucleoid-Associated HU Proteins Are -Terminally Acetylated.

Here we report that the Typhimurium NatB (NatB) protein -terminal acetyltransferase acetylated the -terminal methionine of the nucleoid-associated HU proteins. Our findings were supported by an in vitro analysis of acetylation of the HUα and HUβ proteins and lysine-null (K-null) variants, and by an in vivo analysis of the effect of acetylation on HU-mediated transcriptional regulation of a known target of HU, the promoter. NatB did not acetylate the initiating methionines of HU proteins that were oxidized to methionine sulfoxide, but the reduction of these methionine sulfoxide residues restored the acetylation of HU proteins by NatB. These results demonstrate that the HU proteins are bona fide substrates for the methionine sulfoxide reductases MsrA and MsrB. Finally, we showed that the acetyltransferase, YfmK, is a functional homolog of NatB, and that YfmK acetylates the amino group of the initiating methionine of the HU protein (HBsu).