Forms part of a macromolecular complex that catalyzes the attachment of specific amino acids to cognate tRNAs during protein synthesis. ATP + L-arginine + tRNA(Arg) = AMP + diphosphate + L-arginyl-tRNA(Arg) Monomer; also part of a multisubunit complex that groups tRNA ligases for Arg, Asp, Glu, Gln, Ile, Leu, Lys, Met and Pro. The alpha-helical N-terminus (residues 1-72) mediates interaction with AIMP1 and thereby contributes to the assembly of the multisynthetase complex. Belongs to the class-I aminoacyl-tRNA synthetase family.