ABSTRACT
SARS-CoV-2 virus, the causative agent of Covid-19, has fired up a global pandemic. The virus interacts with the human receptor angiotensin-converting enzyme 2 (ACE2) for invasion via receptor binding domain (RBD) on its spike protein. To provide a deeper understanding of this interaction, we performed microsecond simulations of the RBD-ACE2 complex for SARS- CoV-2 and compared it with the closely related SARS-CoV discovered in 2003. We show residues in the RBD of SARS-CoV-2 that were mutated from SARS-CoV, collectively help make RBD anchor much stronger to the N-terminal part of ACE2 than the corresponding residues on RBD of SARS-CoV. This would result in reduced dissociation rate of SARS-CoV-2 from human recep- tor protein compared to SARS-CoV. This phenomenon was consistently observed in simulations beyond 500 ns and was reproducible across different force fields. Altogether, our study shed light on the key residues and their dynamics at the virus spike and human receptor binding interface and advance our knowledge for the development of diagnostics and therapeutics to combat the pandemic efficiently.