TABLE 2.

Summary of the effects of amino acid substitutions in gp160JR-CSF or gp140JR-FL on 4KG5 recognition

MutantaRegion% WT bindingb
E102AC165
K121AC1 (strand β2)90
T123AC1 (strand β2)50
K171AV2200
F176AV2<1
D180AV27
I184AV22
D185AV230
T198PcC2 (strand β3)1
S199AC2 (strand β3)25
D275VdC2 (D-loop)100
N276AC2 (D-loop)60
R298GeBase of V30.8
N301AV340
N302AV385
P313AV3 crown<1
E322KfV3110
A329KV340
H330ABase of V335
D368AC3100
T388AC350
W395AV410
I423AC40.3
E429AC4100
V430AC42
K432AC450
T455AC4150
N461AV525
R469AC530
G473AC5100
D474AC5100
  • a Amino acid numbering is relative to HIV-1HxB2, where 1 is the initial methionine (29). All mutants are in a gp160JR-CSF background except mutants T198P, D275V, R298G, and E322K, which are in a gp140JR-FL background.

  • b Apparent affinities were calculated as the antibody concentration at half maximal binding. Apparent affinities relative to wild-type (WT) gp140/gp160 were calculated by using the formula: [(apparent affinity of wild type)/(apparent affinity of mutant)] × 100%. The mutants for which 4KG5 binding to gp120 was diminished were tested against MAb 2G12, and 2G12 binding was not significantly changed (data not shown). Mutants for which the apparent affinity of 4KG5 relative to the wild type was <10% are shown in bold.

  • c A T198P substitution was previously determined to affect the interaction between the V1/V2 and V3 loops (94).

  • d A D275V substitution was found to affect an interaction between the V3 loop and the C2 region of gp120 (10).

  • e An R298G substitution has been found to enhance binding of CD4, the anti-CD4bs MAb F105, and anti-V3 loop MAbs to gp120 (90). We determined that the binding of IgG1 b12 to this R298G mutant is only ∼10% of wild-type levels, whereas the binding of several other anti-CD4bs and anti-V3 loop MAbs is equal to or greater than wild-type levels.

  • f The type of charge on the side chain of the residue at position 322 has been associated with coreceptor usage (11/25 rule) (26).