使用分子力学、分子动态学以及量子化学计算方法，对天然的昆虫抗冻蛋白质分子(TmAFP)以长轴平行的方式发生二体相互作用的可能模式进行了系统研究．分子模拟的结果表明，在可能的相互作用模式中，其相互作用区域必须至少包含一个β-面，并且当蛋白单体均取β-面靠近时，其侧链上的羟基在空间的分布满足结构上的二维匹配；利用分子力学与量子化学相结合的方法得到的结果表明两单体的β-面之间具有相对最强的相互作用，同时，高级别的DFT计算以及van der Waals键电荷密度分析进一步证实β-面的相互识别主要表现为β-面的一个苏氨酸侧链的羟基对另一个的苏氨酸羟基氧的识别，即它们之间能形成较强的氢键．因此，分子力学以及量子化学的计算结果都说明蛋白单体在相互识别的过程中，均以β-面相互作用的可能性最大．
The possible interaction models for an antifreeze protein from Tenebrio molitar (TmAFP) have been systematically studied using the methods of molecular mechanics, molecular dynamics and quantum chemistry. It is hoped that these approaches would provide insights into the nature of interaction between protein monomers through sampling a number of interaction possibilities and evaluating their interaction energies between two monomers in the course of recognition. The results derived from the molecular mechanics indicate that monomer's β-sheets would be involved in interaction area and the side chains on two β-faces can match each other at the two-dimensional level. The results from molecular mechanics and ONIOM methods show that the strongest interaction energy could be gained through the formation of H-bonds when the two β-sheets are involved in the interaction model. Furthermore, the calculation of DFT and analysis of van der Waals bond charge density confirm further that recognition between the two TCTs mainly depends on inter-molecular hydroxyls. Therefore, our results demonstrate that during the course of interaction the most favorable association of TmAFPs is via their β-sheets.
YANG Zuoyin, JIA Zongchao, LIU Ruozhuang & CHEN GuangjuDepartment of Chemistry, Beijing Normal University, Beijing 100875, China
