Figure 6.

S-protein RBD determinants of efficient association with human ACE2. (A) Table listing amino-acid differences among the RBDs of the S proteins of the indicated isolates. Residues critical to the differential association of these RBDs with palm-civet and human ACE2 are shown in gray. (B) Experiment similar to that shown in Figure 5B except that individual residues within the TOR2 RBD have been altered to the corresponding residues in the SZ3 RBD. (C) HIV-1-luciferase pseudotyped with S protein of the TOR2, GD, or SZ3 viruses, or with the indicated SZ3 or TOR2 variant, was incubated with HEK293T cells transfected with plasmid encoding human ACE2 or with palm-civet ACE2. Infection, measured as luciferase activity of cell lysates, was assayed 2 days postinfection. The figure shows the mean and range of two experiments.