静电和疏水效应对SARS冠状病毒3CL蛋白酶二聚体稳定性的影响

Effects of Electrostatic and Hydrophobic Interaction on the Stability of SARS Coronavirus 3CL Proteinase Dimer

从 TGEV 3 CL蛋白酶二聚体结构出发 ,研究了 TGEV 3 CL蛋白酶二聚体单体之间的静电和疏水相互作用 .蛋白质的静电相互作用通过有限差分方法求解 Poisson-Boltzmann方程得到 ,疏水相互作用通过分析溶剂可及性表面模型得到 .考察了不同 p H值对 SARS3 CL蛋白酶二聚体静电和疏水相互作用的影响 ,在p H=5 .5～ 8.5时 ,二聚体静电相互作用能、静电去溶剂化能和疏水自由能都具有较小的数值 ,表明在该条件下静电和疏水相互作用有利于二聚体的稳定存在 .由于 SARS 3 CL蛋白酶活性模式为二聚体 ,因此 ,在该p H值范围内 ,有利于蛋白酶保持活性 .在 p H=7.0条件下 ,蛋白酶单体之间具有最强的静电和疏水相互作用 ,从而使蛋白酶具有最强的活性 ,这与实验结果相一致 .p H值对静电去溶剂化能的影响大于疏水自由能 ,表明静电作用是造成强酸或强碱条件下二聚体不能稳定存在的主要原因 .

The crystal structure of the SARS 3CL proteinase was used to study the electrostatic and hydrophobic interactions between two monomers. Solving the Poisson-Boltzmann equation the finite difference method was used to calculate the electrostatic potential. The solvent accessible surface model was supplied for the molecular surface and hydrophobicity. The electrostatic and hydrophobic interactions were explored under the condition of different pH values. The results indicated that the electrostatic interaction energy, electrostatic desolvation free energy and hydrophobic desolvation free energy showed smaller values when pH values are between 5.5 and 8.5, which indicated that, under the condition, the electrostatic and hydrophobic interaction were favorable to the stability of SARS 3CL proteinase dimer. For the dimer was the active form of the SARS 3CL proteinase, the pH condition was good for retaining the activity of the enzyme. The proteinase had the highest activity at around pH= 7.0 for the strongest electrostatic and hydrophobic interaction, which was consistent with the experimental results. pH values had more influence on the electrostatic desolvation free energy than on the hydrophobic desolvation free energy, which implied that the electrostatic interaction was the key factor to the instability of SARS 3CL proteinase dimer under acidic or alkali condition.