Fig. 3.

Measuring RBD attachment on primate ACE2 variants. (A) RBD attachment activity measured on 9 human and 27 nonhuman primate ACE2 variants. The maximum bioluminescence signal measured in the RBD attachment assay for each variant was normalized by that of wild-type ACE2. Data are mean ± SEM of at least three replicates. (B) Intracellular protein expression levels of 27 single primate ACE2 variants, 2 double mutants, and 1 triple mutant were confirmed by western blotting. Expressions of two independent constructs for each variant were shown.