PROS1 and infection: We also showed that missense mutations on N-linked glycosylation sites would destabilize SARS-CoV-1 S. The analysis of viral isolates from 2002 to 2003 and 2003–2004 showed that residue changes N479K, L472P, and F360S destabilized the S protein of 2003–2004 viral isolate leading to a reduction in infection rate.