Submitted to: Journal of Proteomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2012
Publication Date: 2/21/2013
Citation: Wu, X., Vellaichamy, A., Wang, D., Zamdborg, L., Kelleher, N., Huber, S.C., Zhao, Y. 2013. Differential lysine acetylation profiles of Erwinia amylovora strains revealed by proteomics. Journal of Proteomics. 79:60-71. Interpretive Summary: Lysine acetylation is a dynamic and reversible modification of proteins that was thought until recently to be restricted to only certain proteins in the cell nucleus. However, we now know that it occurs in many cellular compartments and that many different proteins are acetylated. Lysine acetylation has been documented in several bacteria, including Escherichia coli and Salmonella enterica, but no studies of lysine acetylation in plant pathogenic bacteria have been reported so far. In the present study, we show that numerous proteins are acetylated in two strains of Erwinia amylovora. The extent of lysine acetylation varied with growth conditions and growth stage, and also differed between two strains of E. amylovora that display differential virulence in plants. Numerous proteins involved in metabolism and virulence were found to be lysine acetylated. Overall the findings reinforce the notion that lysine acetylation of proteins is regulated in plant pathogenic bacteria. It is also possible that lysine acetylation may explain differences in virulence among strains of E. amylovora, which causes fire blight disease, an economically important plant disease of the Rosaceae crops, including apples, pears and raspberries. The disease costs millions of dollars of crop losses annually around the world and its control has become a major concern for apple and pear industry.
Technical Abstract: Protein lysine acetylation (LysAc) in bacteria has recently been demonstrated to be widespread in E. coli and Salmonella and to broadly regulate bacterial physiology and metabolism. However, LysAc in plant pathogenic bacteria is largely unknown. Here we report the lysine acetylome of Erwinia amylovora, an enterobacterium causing serious fire blight disease of apples and pears. Immuno-blots using generic anti-lysine acetylation antibodies and comparative proteomic analysis demonstrated that growth conditions strongly altered the LysAc profile in E. amylovora. Differential LysAc profiles were also observed for two E. amylovora strains that are known to display differential virulence in plants. Proteomic analysis of LysAc in E. amylovora identified 141 LysAc sites on 96 proteins that function in a wide range of biological pathways. Among them, 44% of the proteins are involved in metabolic processes, including central metabolism, and lipopolysaccharide, nucleotide, and amino acid metabolism. For the first time, several proteins involved in E. amylovora virulence were found to be lysine acetylated, including expolysaccharide amylovoran biosynthesis- and type III secretion-associated proteins. Comparative analysis revealed that 20 LysAc sites on 17 proteins and nine LysAc sites on eight proteins were commonly identified in two E. amylovora strains, and in both E. coli and E. amylovora, respectively. In addition, 77 LysAc proteins in E. amylovora strains were further identified by IEF-2DE gel and MALDI-TOF, in which 17 proteins were commonly identified by LC-MS/MS. Collectively, these results reinforce the notion that LysAc of proteins is widespread in bacterial metabolism and also suggest that LysAc may play a role in bacterial virulence.