gp120 is a glycoprotein exposed on the surface of the HIV envelope. The 120 in its name comes from its molecular weight of 120 kilodaltons. The crystal structure of gp120 complexed to D1D2 CD4 and a neutralizing antibody Fab was solved by Peter Kwong in 1998. It is organized with an outer domain, an inner domain with respect to its termini and a bridging sheet. The gp120 gene is around...