Efffects of electrostatic and hydrophobic interaction on the stability of the TGEV main proteinase dimer

The crystal structures of the TGEV 3CL proteinase is used to study the electrostatic and hydrophobic interactions between two monomers. Solving the Poisson-Boltzmanne equation using the finite difference method is used to calculate the electrostatic potential. The solvent accessible surface model is supplied for the molecular surface and hydrophobicity. The electrostatic and hydrophobic interactions are explored in the condition of different pH values. The electrostatic interaction energy, electrostatic desolvation free energy, and hydrophobic desolvation free energy show smaller values when pH values are between 5.5 and 8.5, which indicates that, in the condition, the electrostatic and hydrophobic interaction are favorable to the stability of the TGEV 3CL proteinase dimer. The results are consistent with the experimental condition for the crystallization of the TGEV 3CL proteinase dimer. pH values have stronger influence on the electrostatic desolvation free energy than on the hydrophobic desolvation free energy, which implies that the electrostatic interaction is the key factor to the instability of the TGEV 3Cl proteinase dimer in acid or alkali condition.