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.