FIGURE 1.

Validation of pseudovirus preparation and ACE2 expression. (a) Schematic structure of the spike protein of SARSr‐CoVs (upper panel) and alignment of the amino acid sequences of the receptor‐binding motifs (RBMs) of SARS‐CoV, SARS‐CoV‐2 and pangolin‐CoV spike proteins (lower panel). (b) Western blot detection of spike proteins of SARS‐CoV‐BJ01, SARS‐CoV‐2 and pangolin‐CoV in the pseudovirus stock solutions using an antibody against the HA tag conjugated to the viral spike proteins. HIV‐1 p24, a protein of the carrier pseudovirus, was detected as the loading control. "Mock" indicates the cells without any treatment. "NC" indicates the cells packaging the negative‐control pseudovirus that does not carry any spike. (c) Detection of different ACE2 orthologs in HeLa cells after transfecting the corresponding plasmids using an antibody against the 6XHis tag conjugated to the ACE2 proteins. β‐actin was detected as the loading control. All the Western blots were repeated for three times and the results were subjected to densitometric measurement to quantify the intensity of the bands using ImageJ program. [Colour figure can be viewed at wileyonlinelibrary.com]