Structural conservation among variants of the SARS-CoV-2 spike postfusion bundle

Significance Emergence of viral pathogens necessitates new approaches to study viral fusion and entry into host cells. A key step in mediating fusion involves the formation of a six-helix bundle within the spike protein. Rapid structural characterization of this state has been difficult, hindering understanding of emerging variants. We developed a method to efficiently determine high-resolution bundle structures by molecular scaffolding and cryogenic electron microscopy. Using this method, we determined bundle structures of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants. These structures reveal local effects of mutations on HR1HR2 interactions but global conservation of the bundle architecture among SARS-CoV-2 variants. We predict that inhibitors disrupting the postfusion bundle might be broadly efficacious against variants and even more distantly related lethal viruses.