FIG. 2.

Binding of sCD4 to HIV-1 envelope glycoproteins. COS-1 cells were transfected with plasmids expressing either the HXBc2 or YU2 envelope glycoproteins and metabolically labeled. Soluble CD4 was bound at room temperature for 90 min, and the amount of sCD4 bound was determined by immunoprecipitation of the sCD4-envelope glycoprotein complexes with the OKT4 anti-CD4 antibody. Data were normalized for the cell surface expression of each envelope glycoprotein as described in the legend to Fig. 1.