Catalyzes the formation of the pentaglycine interpeptide bridge, which is characteristic of the S.aureus peptidoglycan. Adds glycines 2 and 3 of the pentaglycine bridge, using glycyl-tRNA(Gly) as donor (By similarity). beta-D-GlcNAc-(1->4)-Mur2Ac(oyl-L-Ala-D-isoglutaminyl-L-Lys-(N(6)-Gly)-D-Ala-D-Ala)-di-trans,octa-cis-undecaprenyl diphosphate + 2 glycyl-tRNA(Gly) = 2 H(+) + MurNAc-L-Ala-D-isoglutaminyl-L-Lys-(N(6)-tri-Gly)-D-Ala-D-Ala-diphospho-di-trans,octa-cis-undecaprenyl-GlcNAc + 2 tRNA(Gly) Homodimer. Interacts with FemB (By similarity). Belongs to the FemABX family.