N-terminal residues 105-117 of HIV-1 gp120 are not involved in CD4 binding.

Syu et al. recently reported that deletion of residues Ile-108 to Leu-116 from the amino terminus of gp120 abolished CD4 binding. The authors have investigated the role of this region using a monospecific antipeptide antibody. As assessed by a microtiter plate-based radioimmunoassay, the antibody, raised in sheep against a synthetic peptide encompassing this deleted region, does not inhibit the gp120-CD4 association. The reported loss of CD4 binding ability, resulting from the deletion in this region of gp120, is likely to be due to indirect structural changes in gp120 rather than representing an integral part of the CD4 binding domain.