title: Conformational Flexibility of a Short Loop near the Active Site of the SARS-3CLpro is Essential to Maintain Catalytic Activity.
abstract: The SARS 3C-like proteinase (SARS-3CLpro), which is the main proteinase of the SARS coronavirus, is essential to the virus life cycle. This enzyme has been shown to be active as a dimer in which only one protomer is active. However, it remains unknown how the dimer structure maintains an active monomer conformation. It has been observed that the Ser139-Leu141 loop forms a short 3(10)-helix that disrupts the catalytic machinery in the inactive monomer structure. We have tried to disrupt this helical conformation by mutating L141 to T in the stable inactive monomer G11A/R298A/Q299A. The resulting tetra-mutant G11A/L141T/R298A/Q299A is indeed enzymatically active as a monomer. Molecular dynamics simulations revealed that the L141T mutation disrupts the 3(10)-helix and helps to stabilize the active conformation. The coil-3(10)-helix conformational transition of the Ser139-Leu141 loop serves as an enzyme activity switch. Our study therefore indicates that the dimer structure can stabilize the active conformation but is not a required structure in the evolution of the active enzyme, which can also arise through simple mutations.
authors.affiliation: BNLMS, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China.|Center for Quantitative Biology, Peking University, Beijing, 100871, China.
authors.forename: Chunmei
authors.initials: C
authors.lastname: Li
authors.affiliation: BNLMS, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Teng
authors.affiliation: Center for Quantitative Biology, Peking University, Beijing, 100871, China.
authors.forename: Yifei
authors.initials: Y
authors.lastname: Qi
authors.affiliation: BNLMS, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China.
authors.forename: Bo
authors.initials: B
authors.lastname: Tang
authors.affiliation: BNLMS, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China.
authors.forename: Hailing
authors.initials: H
authors.lastname: Shi
authors.affiliation: Center for Quantitative Biology, Peking University, Beijing, 100871, China.
authors.forename: Xiaomin
authors.initials: X
authors.lastname: Ma
authors.affiliation: BNLMS, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China.|Center for Quantitative Biology, Peking University, Beijing, 100871, China.
authors.forename: Luhua
authors.initials: L
authors.lastname: Lai
mesh_terms: D020816:Amino Acid Motifs; D002384:Catalysis; D020134:Catalytic Domain; D000086782:Coronavirus 3C Proteases; D003546:Cysteine Endopeptidases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004789:Enzyme Activation; D057927:Hydrophobic and Hydrophilic Interactions; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D009154:Mutation; D011487:Protein Conformation; D055503:Protein Multimerization; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014764:Viral Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D021122:Protein Subunits; D014764:Viral Proteins; D003546:Cysteine Endopeptidases; D000086782:Coronavirus 3C Proteases