The DRS-AIMP2-EPRS subcomplex acts as a pivot in the multi-tRNA synthetase complex

Aminoacyl-tRNA synthetases (ARSs) play essential roles in protein biosynthesis as well as in other cellular processes, often using evolutionarily acquired domains. For possible cooperativity and synergistic effects, nine ARSs assemble into the multi-tRNA synthetase complex (MSC) with three scaffold proteins: aminoacyl-tRNA synthetase complex-interacting multifunctional proteins 1, 2 and 3 (AIMP1, AIMP2 and AIMP3). X-ray crystallographic methods were implemented in order to determine the structure of a ternary subcomplex of the MSC comprising aspartyl-tRNA synthetase (DRS) and two glutathione S-transferase (GST) domains from AIMP2 and glutamyl-prolyl-tRNA synthetase (AIMP2_GST and EPRS_GST, respectively). While AIMP2_GST and EPRS_GST interact via conventional GST heterodimerization, DRS strongly interacts with AIMP2_GST via hydrogen bonds between the α7-β9 loop of DRS and the β2-α2 loop of AIMP2_GST, where Ser156 of AIMP2_GST is essential for the assembly. Structural analyses of DRS-AIMP2_GST-EPRS_GST reveal its pivotal architecture in the MSC and provide valuable insights into the overall assembly and conditionally required disassembly of the MSC.