ABSTRACT
The global coronavirus disease 2019 (COVID-19) pandemic, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has led to an unprecedented worldwide public health emergency. Despite the concerted efforts of the scientific field, by April 25, 2021, SARS-CoV-2 had spread to over 192 countries/regions, causing more than 146 million confirmed cases including 31 million deaths. For now, an established treatment for patients with COVID-19 remains unavailable. The key to tackling this pandemic is to understand the mechanisms underlying its infectivity and pathogenicity. As a predominant focus, the coronavirus spike (S) protein is the key determinant of host range, infectivity, and pathogenesis. Thereby comprehensive understanding of the sophisticated structure of SARS-CoV-2 S protein may provide insights into possible intervention strategies to fight this ongoing global pandemic. Herein, we summarize the current knowledge of the molecular structural and functional features of SARS-CoV-2 S protein as well as recent updates on the cell entry mechanism of the SARS-CoV-2, paving the way for exploring more structure-guided strategies against SARS-CoV-2.