Abstract
Lysine acetylation is a prevalent post-translational modification in both eukaryotes and prokaryotes. Whereas this modification is known to play pivotal roles in eukaryotes, the function and extent of this modification in prokaryotic cells remain largely unexplored. Here we report the acetylome of a pair of antibiotic-sensitive and -resistant nosocomial pathogen Acinetobacter baumannii SK17-S and SK17-R. A total of 145 lysine acetylation sites on 125 proteins was identified, and there are 23 acetylated proteins found in both strains, including histone-like protein HU which was found to be acetylated at Lys13. HU is a dimeric DNA-binding protein critical for maintaining chromosomal architecture and other DNA-dependent functions. To analyze the effects of site-specific acetylation, homogenously Lys13-acetylated HU protein, HU(K13ac) was prepared by genetic code expansion. Whilst not exerting an obvious effect on the oligomeric state, Lys13 acetylation alters both the thermal stability and DNA binding kinetics of HU. Accordingly, this modification likely destabilizes the chromosome structure and regulates bacterial gene transcription. This work indicates that acetyllysine plays an important role in bacterial epigenetics.
Highlights
Post-translational modifications can confer novel properties to the modified proteins, including changes in enzymatic activity, subcellular localization, interaction partners, protein stability, and DNA-binding ability
Strain SK17-S isolated first from a male hospitalized patient is susceptible to antibiotic imipenem, whereas strain SK17-R isolated later from the same patient is resistant to this antibiotic
It is noteworthy that only four identical acetylation sites were previously reported in A. baumannii ATCC19606 harvested at stationary phase (Kentache et al, 2016), including DNA-binding protein HU (Table S1)
Summary
Post-translational modifications can confer novel properties to the modified proteins, including changes in enzymatic activity, subcellular localization, interaction partners, protein stability, and DNA-binding ability. The global lysine acetylation profiles have been brought out in many prokaryotes including Bacillus subtilis (Kim et al, 2013), Cyanobacterium Synechocystis (Mo et al, 2015; Chen et al, 2017), Escherichia coli (Zhang et al, 2013; Castano-Cerezo et al, 2014), Mycobacterium tuberculosis (Xie et al, 2015; Ghosh et al, 2016), Salmonella enterica (Wang et al, 2010), Streptomyces roseosporus (Liao et al, 2014), Thermus thermophilus (Okanishi et al, 2013), Vibrio parahemolyticus (Pan et al, 2014), etc Based on these studies, the acetylated proteins appeared to be widespread in prokaryotes and participated in most classes of cellular processes including adaptation and virulence (Ouidir et al, 2016). Understanding the effects of site-specific lysine acetylation of prokaryotic proteins becomes an essential task in medicinal microbiology research
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