The SARS-CoV-2 virus has now become one of the greatest causes of infectious death and morbidity since the 1918 flu pandemic. Substantial and unprecedented progress has been made in the elucidation of the viral infection process in a short time; however, our understanding of the structure-function dynamics of the spike protein during the membrane fusion process and viral uptake remains incomplete. Employing computational approaches, we use full-length structural models of the SARS-CoV-2 spike protein integrating Cryo-EM images and biophysical properties, which fill the gaps in our understanding. We propose a membrane fusion model incorporating structural transitions associated with the proteolytic processing of the spike protein, which initiates and regulates a series of events to facilitate membrane fusion and viral genome uptake. The membrane fusion mechanism highlights the notable role of the S1 subunit and eventual mature spike protein uptake through the host membrane. Our comprehensive view accounts for distinct neutralizing antibody binding effects targeting the spike protein and the enhanced infectivity of the SARS-CoV-2 variant.
Keywords: COVID-19; S protein; SARS-CoV-2; coronavirus; fusion mechanism; membrane fusion; spike protein; viral entry.