Bifunctional glutamate/proline--tRNA ligase (EPRS1)

Multifunctional protein which is primarily part of this aminoacyl-tRNA synthetase multienzyme complex, also know as multisynthetase complex, that catalyzes the attachment of the cognate amino acid into the corresponding tRNA in a two-step reaction: the amino acid is first activated by ATP to form a covalent intermediate with AMP and is then transferred to the acceptor end of the cognate tRNA (PubMed:1756734, PubMed:24100331, PubMed:23263184). The phosphorylation of EPRS, triggered by interferon-gamma, dissociates the protein in the aminoacyl-tRNA synthetase multienzyme complex and recruits it to the GAIT complex that binds to stem loop-containing GAIT elements in the 3'-UTR of diverse inflammatory mRNAs (such as ceruplasmin), suppressing their translation.

Interferon-gamma can therefore divert, in specific cells, the EPRS function from protein synthesis to translation inhibition (PubMed:15479637, PubMed:23071094). Also functions as an effector of this mTORC1 signaling pathway by promoting, through SLC27A1, the uptake of long-chain fatty acid by adipocytes.