FIG. 2.

Critical roles of SIVmac Vif K27 and SIVagm Vif K28 residues in neutralizing A3G, but not A3F. (A) N-terminal amino acid sequence alignment of Vif proteins from HIV-1, HIV-2, SIVcpz, SIVmac239, and three SIVagm isolates. Three lysines (K22, K26, and K34) are indicated. (B) Expression of SIVmac Vif K27A and SIVagm Vif K28A mutants. SIV Vif proteins were expressed from the HIV-1 subgenomic expression vector pNL-A1, and protein expression was determined in 293T cells by Western blotting with an anti-HA antibody. (C) Activities of SIV Vif K27A and K28A mutants. 293T cells were transfected with pNL-LucΔenvΔvif, an indicated SIV Vif expression vector, a VSV-G expression vector, and either an A3F or A3G expression vector. Vif activities were determined by measuring the infectivity of HIV-1Δvif virus as for Fig. 1B. The standard errors of the means (error bars) were calculated from three independent experiments.