Cryo-electron microscopy structure of the SADS-CoV spike glycoprotein provides insights into an evolution of unique coronavirus spike proteins

Guan, Hongxin; Wang, Youwang; Saeed, Abdullah F.U.H.; Li, Jinyu; Perčulija, Vanja; Li, Yu; Zhu, Ping; Ouyang, Songying

The outbreak of a novel betacoronavirus (SARS-CoV-2) has aroused great public health concern. As a new coronavirus which was responsible for a large-scale outbreak of fatal disease in piglets in China, swine acute diarrhea syndrome coronavirus (SADS-CoV) originated from the same genus of horseshoe bats (Rhinolophus) as SARS-CoV and possesses a broad species tropism. In addition to human cells, it can also infect cell lines from diverse species. Given the importance of the spike glycoprotein (S) protein in viral entry and host immune responses, here we report the cryo-EM structure of the SADS-CoV S in the prefusion conformation at a resolution of 3.55 Ã…. Our studies reveal that SADS-CoV S structure takes an intra-subunit quaternary packing mode where the NTD and CTD from the same subunit pack together by facing each other. The comparison of NTD and CTD with that of the other four genera gives the suggestion of the evolutionary procedure of the SADS-CoV S. Moreover, SADS-CoV S has several characteristic structural features, i.e., more compact architecture of S trimer, masking of epitopes by glycan shielding, which may facilitate to viral immune evasion. These data provide new insights into the evolutionary relationships of SADS-CoV S and would deepen our understanding of their structural and functional diversity which will facilitate to vaccine development.