Identification of Aspartyl-tRNA Synthetase as Co-purifying with Wheat Germ eIF2

Eukaryotic translation initiation factor 2 (eIF2) is among the best-studied of the translation initiation factors, but early preparations from wheat germ consistently showed a co-purifying protein of ~61kDa. As this protein was never identified, we revisited the question of its identity using mass spectrometry on an archived Coomassie-stained and dried gel of eIF2 purified in 1991. The co-purifying protein, aspartyl-tRNA synthetase, is notable for serving as a receptor for the R enantiomer of β-aminobutyric acid, with links to stress-induced eIF2α phosphorylation, highlighting the potential for stable "super complexes" connecting translation initiation with stress responses.