TABLE 2.

Ligand-binding characteristics of wild-type YU2 and mutant derivativesa

Envelope proteinRelative binding
sCD4CD4i antibody 17bCD4BS antibodies
F10515eIgG1b1221hF91
Wild type1.001.001.001.001.001.001.00
112 W/A0.590.940.220.540.970.830.91
255 V/W0.380.880.000.060.510.800.76
257 T/A0.690.840.000.160.771.100.81
273 R/W0.780.910.720.900.460.780.76
375 S/W1.740.900.000.000.020.320.00
375 S/F1.100.700.000.220.570.720.31
375 S/Y1.131.080.000.680.900.910.45
377 N/L0.951.021.120.981.010.810.85
423 I/P0.090.051.010.851.270.830.86
423 I/M + 425 N/K + 431 G/E0.000.001.250.561.181.250.65
447 S/I0.000.750.000.760.580.840.38
481 S/F0.690.800.460.840.730.730.73
  • a The indicated residue changes were introduced into the YU2 wtΔ protein. The radiolabeled proteins were expressed in 293T cells and precipitated by a polyclonal mixture of sera from HIV-1-infected individuals, by a combination of sCD4 and the T45 anti-CD4 antibody, or by monoclonal antibodies. The precipitated proteins were resolved by SDS-PAGE and autoradiography. The amounts of precipitated proteins were determined by PhosphorImager analysis (Molecular Dynamics). The relative binding value shown was calculated as follows: (mutant protein/wtΔ protein)ligand × (wtΔ protein/mutant protein)serum mixture. The values represent the average obtained from at least two independent experiments; relative binding in the experiments exhibited less than 25% variation from the values reported.