K88 Acetylation Regulates PhoP Activity And Screening Of Putative Transcriptional Regulators In Salmonella

The two-component system PhoP/PhoQ regulates about 5% genes in Salmonella enterica serovar Typhimurium.PhoP/PhoQ is highly conserved in bacteria,thus underlines its importance to S.Typhimurium virulence.Mass spectrometry analysis showed that the conserved lysine residue 88?K88?can be acetylated.According to PhoP crystal structure from M.Tuberculosis,the K88 is located at ?4-?5-?5 region,which is crucial to PhoP dimerization.Firstly,we confirmed the acetylation of K88.K88 acetylation level showed no apparent decrease in pat KO strain.Moreover,when we incubated PhoP with AcP in vitro,K88 acetylation level increased along with AcP concentration.Acetylation of K88?mimicked by glutamine substitute?increased the ability of PhoP dimerization and up-regulated the expression of phoP and its downstream genes.Deacetylation of K88?mimicked by arginine substitute?was more beneficial to S.Typhimurium colonization,and fetal to mice.Immunohistochemistry analysis showed K88 R caused severer enteritis.To sum up,deacetylation of K88 facilitates S.Typhimurium infection to host.Besides,intermediate metabolite AcP can be used as phosphate donor.PhoP K88 Q can no longer be phosphorylated by AcP,which indicates that different modifications can interact with each other,thus regulate S.Typhimurium virulence.Besides,we analyzed genome informatics and picked out 30 putative transcriptional regulators.Knock-out strains of candidate genes were then screened by acid tolerance response and cell model successively.It turns out that STM14₂717 was involved in all three processes.While RT-PCR showed there's no significant difference of phoP transcription level between ?STM14₂717 and wild type strain.This indicates STM14₂717 might participate in other pathways.