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 monomer structure of nsp4C mutant C425S. Both WT nsp4C and the C425S mutant contain two monomers in one asymmetric unit, and the conformation of the WT and mutant monomers are quite similar, with a root mean square deviation (r.m.s.d.) between equivalent Ca atoms of less than 1.0 Ã… . The major differences arise from three regions in the monomer (Fig. 3D ). The first is the loop from Ser449 to Met452 which forms an additional b-strand b3 in the C425S mutant; interaction of this region with the C-terminal of the monomer in the mutant dimer produces this deviation. The second region is located between Asn476-Asn479, which is formed by interaction with symmetry related molecules as a result of crystal packing (Fig. 3D ). The third occurs in the C-termini of the monomers, where an additional bstrand b4 in the mutant monomer is observed with detectable electron density from Ser493 to Leu495, while the equivalent region of the wild-type monomer exists as a long loop.