Structural and biochemical characterization of nsp12-nsp7-nsp8 core polymerase complex from SARS-CoV-2

Peng, Qi; Peng, Ruchao; Yuan, Bin; Zhao, Jingru; Wang, Min; Wang, Xixi; Wang, Qian; Sun, Yan; Fan, Zheng; Qi, Jianxun; Gao, George F.; Shi, Yi

Summary The ongoing global pandemic of coronavirus disease 2019 (COVID-19) has caused a huge number of human deaths. Currently, there are no specific drugs or vaccines available for this virus (SARS-CoV-2). The viral polymerase is a promising antiviral target. Here, we describe the near-atomic resolution structure of the SARS-CoV-2 polymerase complex, consisting of nsp12 catalytic subunit and nsp7-nsp8 cofactors. This structure highly resembles the counterpart of SARS-CoV with conserved motifs for all viral RNA-dependent RNA polymerases, and suggests the mechanism for activation by cofactors. Biochemical studies reveal reduced activity of the core polymerase complex and lower thermostability of individual subunits of SARS-CoV-2 as compared to that of SARS-CoV. These findings provide important insights into RNA synthesis by coronavirus polymerase and indicate a well adaptation of SARS-CoV-2 towards humans with relatively lower body temperatures than the natural bat hosts.