Cell lines and plasmids
HEK293T and HeLa cells were obtained from the American Tissue Culture Collection and cultured in Dulbecco’s modified Eagle medium (DMEM) (Gibco, USA) supplemented with 10% fetal bovine serum (FBS) in a humidified 5% CO2 incubator at 37°C.
Full-length SARS-CoV-2 spike (GenBank accession number MN908947.3), SARS-CoV BJ01 spike (GenBank accession number AY278488.2) and Pangolin CoV GD1 spike (GISAID accession number: EPI_ISL_410721) were all synthesized by Sangon and subcloned into the pcDNA3.1 vectors with a C-terminal HA tag. The cDNAs encoding different ACE2 proteins (Table S1) were synthesized by Sangon and subcloned into pcDNA3.1 vectors with a C-terminal His tag. All the plasmids were verified by Sanger sequencing.