The accomplices: Heparan sulfates and N-glycans foster SARS-CoV-2 spike:ACE2 receptor binding and virus priming

Summary The SARS-CoV-2 spike glycoprotein mediates virus attachment to human host cells by binding angiotensin-converting enzyme 2 (ACE2) and heparan sulfate (HS) proteoglycans. To elucidate the structure, dynamics, and functional consequences of these interactions, we carried out microsecond-long all-atom molecular dynamics simulations, followed by random acceleration molecular dynamics simulations, of the fully glycosylated spike:ACE2 complex with and without heparin chains bound. We find that heparin, a model for HS, promotes structural and energetic stabilization of the active conformation of the spike receptor binding domain (RBD) and reorientation of ACE2 toward the N-terminal domain in the same spike subunit as the RBD. Spike and ACE2 N-glycans exert synergistic effects, promoting better packing, strengthening the protein:protein interaction, and prolonging the residence time of the complex. ACE2 and heparin binding trigger rearrangement of the S2’ functional site through allosteric interdomain communication. HS thus has a multifaceted role in facilitating SARS-CoV-2 infection.