MACV GPC residues D114, S116, D140, K169, and most likely W147 are dispensable for cell attachment and entry of MACV. According to the crystal structure, D114 and S116 form interaction motif 2, which contacts hTfR1 residues N348, S370, and K371. K169, a part of interaction motif 4, contacts K344, and E294 of hTfR1. In our functional assays, using both purified proteins and MoMLV pseudotypes, mutating these residues had no or minimal effect on hTfR1 binding and cell-entry (Figs. 2 and 3), suggesting that although they might contact hTfR1, they by themselves play no significant role in hTfR1 usage by MACV.