Fig. 4.

Identification of gp41 site on gC1qR using gC1qR deletion mutants.

The same strategy as in Fig. 2 was applied in that the deletion mutants that showed consistently diminished binding to gp41-coated wells were selected and compared. Microtiter plate wells were first coated with 2 μg/ml HIV-gp41 (1 h, 37 °C) as described in the legend to Fig. 3 and after washing and blocking, the bound gp41 was reacted (O/N, 4C) with 2.5 μg/ml of biotinylated WT gC1qR or the selected biotinylated gC1qR deletion (Δ) mutants. The single point mutation is indicated as G substitution for W at position 233 (W233G). The position of residues 174–180, which showed significantly reduced binding to gp41 (A), is shown in the gC1qR 3D structure (B). The significance of the data is indicated as: * p ≤ 0.05 and **p ≤ 0.01.