In the initiation step of translation, aminoacyl-tRNA synthetase (aaRS) catalyzes esterification between its cognate amino acid and tRNA to produce aminoacyl-tRNA (aa-tRNA). The 20 aaRSs can be divided into two classes, based on sequence identity and characteristic structural motifs. Both leucyl- and arginyl-tRNA synthetases (LeuRS and ArgRS) belong to class I aaRSs. Some aaRSs are modified by phosphorylation, which influences multidrug tolerance in E. coli and the reactive oxygen species defense mechanism in mammalian cells. However, studies focusing on other forms of PTM（post translational modification） of aaRSs, such as acetylation, are few in number.
Previous proteomic analyses have shown that aminoacyl-tRNA synthetases (aaRSs) in many organisms can be modified by acetylation of lysine (Lys). Recently, Ph. D graduate student Qing YE and her colleagues, under the guidance of Prof. Enduo WANG, at Shanghai Institute of Biochemistry and Cell Biology/Center for Excellence in Molecular Cell Science, the Chinese Academy of Sciences, showed that lysine acetylation could regulate aaRSs’ activity. In detail, they purified overexpressed Escherichia coli LeuRS and ArgRS (EcLeuRS and EcArgRS) in E. coli and identified acetylated Lys residues by mass spectrometry. Glutamine (Gln) scanning mutagenesis revealed that Lys619, Lys624 and Lys809 in EcLeuRS and Lys126 and Lys408 in EcArgRS play important roles in enzyme activity. Furthermore, they utilized a novel protein expression system (pAcKRS) to obtain variants harboring acetylated-Lys (AcK) at specific sites, and investigated their catalytic activity. Acetylation of these Lys residues could affect the corresponding aaRSs’ aminoacylation activity by influencing amino acid activation and the affinity for tRNA. In vitro assays showed that acetyl-phosphate (AcP) nonenzymatically acetylates EcLeuRS and EcArgRS, and suggested the sirtuin class deacetylase CobB could deacetylate these two enzymes. These findings revealed the regulatory role for Lys acetylation/deacetylation in controlling the activity of aaRSs and proposed that acetylation/deacetylation may act as a post-translational switch to influence proteins synthesis.
This work, entitled “Acetylation of lysine ε-amino groups regulates aminoacyl-tRNA synthetase activity in Escherichia coli”, was published online in Journal of Biological Chemistry on Aril 28th, 2017 and was supported by grants from the National Natural Science Foundation of China, the Ministry of Science and Technology of China, and the Chinese Academy of Sciences.
Article Link:
http://www.jbc.org/content/early/2017/04/28/jbc.M116.770826.full.pdf
AUTHOR CONTACT:
WANG Enduo
Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences,
Shanghai, China
Phone: 86-21-54921241; E-mail: edwang@sibcb.ac.cn
Acetylation mechanism on aaRSs mediated by AcP and CobB
AcP nonenzymatically acetylates aaRSs and comprises their aminoacylation activities; this modification could be removed by CobB to maintain aaRSs’ function and cell homeostasis.
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