HPPK is an important kinase as well as an ideal target for developing antimicrobial agents:its role is catalyzing the first reaction in the folate biosynthetic pathway which is indispensable for bacterials. During the catalytic reaction,HPPK first combines with MgATP,and then with HP,only after that,the reaction can occur. The three loops of the enzyme play a key role in this binding process:the binding site of MgATP locates under loop 3 while under that of HP binding locates under loop 2:the opening up and closing down of loops 3 and 2 means the opening up and closing down of binding sites of MgATP and HP respectively. We performed MD simulations to research the conformational change of the binary complex of HPPK and MgATP,which indicates that loop 3 keeps close in all our simulations,while loop 2 transforms between open,semi-open and close conformations. Considering loop 2 is binding site of HP,so the mechanism of HP binding the binary complex is very possibly conformational selection.%HPPK一种是重要的激酶和潜在的抗生素靶点,它的作用是催化细菌体内重要生命物质叶酸合成的第一步反应。在HPPK的催化反应过程中,HPPK先与MgATP结合,再与HP结合,然后催化反应发生。 HPPK中的3个loop结构在结合过程中起着重要作用：MgATP的结合位点位于loop 3下,HP的结合位点位于loop 2下。 loop 3与loop 2的开闭分别意味着MgATP与HP结合位点的开闭,本文运用分子动力学模拟研究HPPK与MgATP复合物构象变化。计算结果表明,在整个模拟过程中loop 3一直处于关闭状态,而loop 2则在全开、半开以及关闭等构象间转换；loop 2的开闭意味着HP结合位点的开闭,这些结果揭示了HP进入HPPK-MgATP复合物很可能遵循的是构象选择机制。
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