Crystal Structure of the C-Terminal Cytoplasmic Domain of Non-Structural Protein 4 from Mouse Hepatitis Virus A59

Xu, Xiaoling; Lou, Zhiyong; Ma, Yanlin; Chen, Xuehui; Yang, Zhangsheng; Tong, Xiaohang; Zhao, Qi; Xu, Yuanyuan; Deng, Hongyu; Bartlam, Mark; Rao, Zihe

The electrostatic surface potential of the dimer differs from that of WT nsp4C. The positive and negative charges are distributed equally on the surface, and Glu411 from each monomer are close to each other to form a hole in the middle of the dimer. The intersecting C-termini of the monomers result in a ''closed'' conformation of the mutant dimer (Fig. 1) . The parallel N-termini of the two monomers are much more convenient for the binding of nsp4C to the membrane as a dimer, but this conformation is formed by mutagenesis and it could also be identified in the crystal packing of WT nsp4C (Fig.3D) . Thus the conformation of mutant C425S dimer is not likely to be physiological but instead an artifact of crystallization.