Figure 3.

Overlap between the coreceptor-binding site and the 17b epitope. A space-filling model of gp120 bound to sCD4 is depicted. Residues shown by Rizzuto et al.(17) to decrease CCR5 binding by >50% when mutated while reducing CD4 binding by <50% are colored red (17), contact residues for 17b are shown in light blue (16), and residues involved in both CCR5 and 17b binding are shown in purple. Although 8x contains numerous mutations in gp120 that contribute to the CD4-independent phenotype [C.C.L., T.L.H., J. Romano, B. S. Haggarty, T. J. Matthews, R.W.D. and J.A.H (unpublished work)], only one mutation in 8x affects a contact site for 17b (I423V, shown in green). The stems of the V1/V2 and V3 loops are colored orange.