Structural basis of the American mink ACE2 binding by Y453F trimeric spike glycoproteins of SARS-CoV-2
Hyunjun Ahn1#, Brenda M. Calderon2,3#, Xiaoyu Fan2,3#, Yunrong Gao1#, Natalie L. Horgan1, Nannan Jiang2,3, Dylan S. Blohm1, Jaber Hossain2,3, Nicole Wedad K. Rayyan1, Sarah H. Osman2,4, Xudong Lin2,3, Michael Currier2,3, John Steel3, David E. Wentworth2,3, Bin Zhou2,3*, Bo Liang1*
1Department of Biochemistry, Emory University School of Medicine, Atlanta, GA, 30322 United States
2COVID-19 Emergency Response, Centers for Disease Control and Prevention, Atlanta, GA 30329
3Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, GA 30329
4Division of Laboratory Sciences, National Center for Environmental Health, Centers for Disease Control and Prevention, Chamblee, GA, 30341
# These authors contributed equally to this study.
* Correspondence: bo.liang@emory.edu and bzhou@cdc.gov
Abstract :
Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) enters the host cell by binding to angiotensin-converting enzyme 2 (ACE2). While evolutionarily conserved, ACE2 glycoproteins differ across various species and differential interactions with Spike (S) glycoproteins of SARS-CoV-2 viruses impact species specificity. Reverse zoonoses led to SARS-CoV-2 outbreaks on multiple American mink (Mustela vison ) farms during the pandemic and gave rise to mink-associated S substitutions known for transmissibility between mink and zoonotic transmission to humans. In this study, we used bio-layer interferometry (BLI) to discern the differences in binding affinity between multiple human and mink-derived S glycoproteins of SARS-CoV-2 and their respective ACE2 glycoproteins. Further, we conducted a structural analysis of a mink variant S glycoprotein and American mink ACE2 (mvACE2) using cryo-electron microscopy (cryo-EM), revealing four distinct conformations. We discovered a novel intermediary conformation where the mvACE2 glycoprotein is bound to the receptor-binding domain (RBD) of the S glycoprotein in a “down” position, approximately 34° lower than previously reported “up” RBD. Finally, we compared residue interactions in the S-ACE2 complex interface of S glycoprotein conformations with varying RBD orientations. These findings provide valuable insights into the molecular mechanisms of SARS-CoV-2 entry.