(Chymo)trypsin-like proteinases 3C-like protease, SARS coronavirus 3C-like proteinase, SARS-CoV-2 Amino Acid Substitution Autolysis COVID-19 Catalytic tetrad Coronavirus 3C Proteases Humans Interdomain loop Mutation, Missense Protein Domains SARS Virus SARS coronavirus SARS-CoV-2 Species Specificity Structural catalytic core Structure-Activity Relationship amino acid substitution chemistry enzymology genetics human missense mutation protein domain species difference structure activity relation