An alignment of consensus sequences (2004) of the amino acid sequence of gp120 was obtained through the HIV sequence database [11] and was analyzed with the N-glycosite software [11] to locate N-glycosylation sites. For our analysis, we did not include the consensus of consensus sequences nor the ancestral sequences, but focused on the consensus sequences for HIV-1 subtypes A1, A2, B, C, D, F1, F2, G, H, CRF01-AE, CRF02-AG, CRF03-AB, CRF04-cpx, CRF06-cpx, CRF08-BC, CRF10-CD, CRF11-cpx, CRF12-BF, and CRF14-BG. The height of the bars indicates the level of conservation among these HIV-1 subtypes. The 7 black bars represent N-glycosylation sites that were found in HIV-1NL4.3 gp120 to be located near a disulphide bridge (directly neighbouring one of the disulphide cysteines or separated by only one amino acid) and were mutated by site-directed mutagenesis.