Acetylation of Lysine ε-amino Groups Regulates Aminoacyl-tRNA Synthetase Activity in Escherichia coli [RNA]

Previous proteomic analyses have shown that aminoacyl-tRNA synthetases (aaRSs) in many organisms can be modified by acetylation of lysine (Lys). In this present study, leucyl-tRNA synthetase and arginyl-tRNA synthetase from Escherichia coli (EcLeuRS and EcArgRS) were overexpressed and purified, and found to be acetylated on Lys residues by mass spectrometry (MS). Glutamine (Gln) scanning mutagenesis revealed that Lys619, Lys624 and Lys809 in EcLeuRS and Lys126 and Lys408 in EcArgRS might play important roles in enzyme activity. Furthermore, we utilized a novel protein expression system to obtain enzymes harboring acetylated-Lys (AcK) at specific sites, and investigated their catalytic activity. Acetylation of these Lys residues could affect their aminoacylation activity by influencing amino acid activation and/or the affinity for tRNA. In vitro assays showed that acetyl-phosphate (AcP) nonenzymatically acetylates EcLeuRS and EcArgRS, and suggested the sirtuin class deacetylase CobB might regulate acetylation of these two enzymes. These findings imply a potential regulatory role for Lys acetylation in controlling the activity of aaRSs and thus protein synthesis.

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