The M Protein of SARS-CoV: Basic Structural and Immunological Properties

Hu, Yongwu; Wen, Jie; Tang, Lin; Zhang, Haijun; Zhang, Xiaowei; Li, Yan; Wang, Jing; Han, Yujun; Li, Guoqing; Shi, Jianping; Tian, Xiangjun; Jiang, Feng; Zhao, Xiaoqian; Wang, Jun; Liu, Siqi; Zeng, Changqing; Wang, Jian; Yang, Huanming

Two other substitutions have been identified, each from a single isolate, in TMI and TMII, respectively. The former (T/G) is a transversion that leads to a residue substitution from Phe to Cys. The latter is a C/T transition leading to residue substitution from Ala to Val. Both Phe and Cys are neutral and weakly acidic with the same pI (pI 5.6). Phe is non-polar (zero charge) and absolutely hydrophobic, whereas Cys is polar and also absolutely hydrophobic. It is expected that the subregional pI (pI 5.60), non-polarity (zero charge) and hydrophilicity (10.5%) will remain unchanged, but the hydrophobicity of TMI might be affected (73.7-68.4%), decreasing the stability to certain extent. It is generally accepted that the hydrophobicity is related to the stability of the membrane structure, and thus might attract the interaction between the virus-origin M protein and the host-origin membrane.