N-Terminal Finger Stabilizes the S1 Pocket for the Reversible Feline Drug GC376 in the SARS-CoV-2 Mpro Dimer

•GC376 binds reversibly to Mpro from both SARS-CoV and SARS-CoV-2.•Nanomolar Ki values were demonstrated for GC376 with both Mpro.•Mpro structures reveal domain swapping via the N-terminus to facilitate drug binding.•These structures provide information on further development of novel antivirals.