Isoleucyl-tRNA synthetase interactome analysis

Aminoacyl-tRNA synthetases (aaRSs) catalyze the ligation of each amino acid to the 3’ hydroxyl group of the cognate tRNA and thereby establish the genetic code for protein synthesis. AaRSs form a complicated network through assembly into a multi-synthetase complex (MSC), which is comprised of nine aaRSs (ArgRS, AspRS, GlnRS, GluProRS, IleRS, LeuRS, LysRS, and MetRS) and three auxiliary proteins (aaRS-interacting multifunctional proteins, p43, p38, and p18 or AIMP1, 2, and 3) in vertebrates. IleRS is one of the least characterized aaRSs in the MSC. It is a class 1a aaRS and has an UNE-I domain at its C-terminal end that is formed by tandem ~90 residue repeats. Systematic depletion and yeast two-hybrid (Y2H) analyses suggest that IleRS binds to the WHEP domain of GluProRS through its UNE-I domain. However, crosslinking and mass spectrometry (XL-MS) analyses revealed that IleRS interacts with ArgRS, LeuRS, and MetRS in the MSC. While such difference may be due to the different dynamic states of the MSC under various cellular environments, it remains to be resolved how IleRS associates with other components of the MSC. Therefore, we performed mass spectrometry analysis to study IleRS interactome using cells expressing wild-type IleRS, C-terminal-deleted IleRS, and the IleRS UNE-I domain alone.