Structural characterization of SARS-CoV-2 dimeric ORF9b reveals potential fold-switching trigger mechanism  

作　　者：Xiyue Jin Xue Sun Yan Chai Yu Bai Ying Li Tianjiao Hao Jianxun Qi Hao Song Catherine CL Wong George F.Gao 

机构地区：[1]School of Life Sciences,Division of Life Sciences and Medicine,University of Science and Technology of China,Hefei 230027,China [2]CAS Key Laboratory of Pathogen Microbiology and Immunology,Institute of Microbiology,Chinese Academy of Sciences,Beijing 100101,China [3]Peking University First Hospital,Peking University,Beijing 100034,China [4]Center for Precision Medicine Multi-Omics Research,Peking University Health Science Center,Peking University,Beijing 100191,China [5]University of Chinese Academy of Sciences,Beijing 100049,China [6]Research Network of Immunity and Health(RNIH),Beijing Institutes of Life Science,Chinese Academy of Sciences,Beijing 100101,China [7]Peking-Tsinghua Center for Life Sciences,Peking University,Beijing 100871,China [8]School of Basic Medical Sciences,Peking University Health Science Center,Peking University,Beijing 100191,China

出　　处：《Science China(Life Sciences)》2023年第1期152-164,共13页中国科学（生命科学英文版）

基　　金：supported by the National Key Research and Development Projects of the Ministry of Science and Technology of China(2020YFC0845900,2021YFC2301300);the Strategic Priority Research Program of the Chinese Academy of Sciences(CAS)(XDB29010202);the National Natural Science Foundation of China(82122040);supported by CAS Project for Young Scientists in Basic Research(YSBR-010);the Youth Innovation Promotion Association CAS。

摘　　要：The constant emergence of severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)variants indicates the evolution and adaptation of the virus.Enhanced innate immune evasion through increased expression of viral antagonist proteins,including ORF9b,contributes to the improved transmission of the Alpha variant;hence,more attention should be paid to these viral proteins.ORF9b is an accessory protein that suppresses innate immunity via a monomer conformation by binding to Tom70.Here,we solved the dimeric structure of SARS-CoV-2 ORF9b with a long hydrophobic tunnel containing a lipid molecule that is crucial for the dimeric conformation and determined the specific lipid ligands as monoglycerides by conducting a liquid chromatography with tandem mass spectrometry analysis,suggesting an important role in the viral life cycle.Notably,a long intertwined loop accessible for host factor binding was observed in the structure.Eight phosphorylated residues in ORF9b were identified,and residues S50 and S53 were found to contribute to the stabilization of dimeric ORF9b.Additionally,we proposed a model of multifunctional ORF9b with a distinct conformation,suggesting that ORF9b is a fold-switching protein,while both lipids and phosphorylation contribute to the switching.Specifically,the ORF9b monomer interacts with Tom70 to suppress the innate immune response,whereas the ORF9b dimer binds to the membrane involving mature virion assembly.Our results provide a better understanding of the multiple functions of ORF9b.

关 键 词：SARS-CoV-2 ORF9b immune escape viral antagonist membrane association fold switch lipid binding 

分 类 号：R373.1[医药卫生—病原生物学]