Exploring the Molecular Origins of Protein Dynamics in the Active Site of Human Carbonic Anhydrase II
Exploring the Molecular Origins of Protein Dynamics in the Active Site of Human Carbonic Anhydrase II
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DOI：
10.1021/jp901321m
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发表时间：
2009-08-20
影响因子：
3.3
通讯作者：
Cheatum, Christopher M.
中科院分区：
文献类型：
--
作者：
Hill, Sarah E.;Bandaria, Jigar N.;Cheatum, Christopher M.
我们提出了与人碳酸酐酶 II (HCA II) 活性位点 Zn 结合的叠氮化物离子和两个单独的活性位点突变体 Thr199 -> Ala (T199A) 和 Leu198 -> Phe (L198F) 的三脉冲振动回波测量。由于蛋白质活性位点的结构运动会影响结合配体的频率，因此从每组数据的全局拟合中获得的频率-频率相关函数 (FFCF) 的时间尺度差异使我们能够推断 HCA II 活性位点动态的时间尺度。令人惊讶的是，删除 T199A 中潜在的静电相互作用导致 FFCF 几乎没有变化，但在 L198F 中插入庞大的苯丙氨酸环会导致动力学更快。我们得出的结论是，相关函数中快速、亚皮秒时间尺度可归因于氢键动力学，而缓慢、明显静态的贡献是由于活性位点中锌结合叠氮化物的构象灵活性。
We present three-pulse vibrational echo measurements of azide ion bound to the active site Zn of human carbonic anhydrase II (HCA II) and of two separate active-site mutants Thr199 -> Ala (T199A) and Leu198 -> Phe (L198F). Because structural motions of the protein active site influence the frequency of bound ligands, the differences in the time scales of the frequency-frequency correlation functions (FFCFs) obtained from global fits to each set of data allow us to make inferences about the time scales Of the active site dynamics of HCA II. Surprisingly, the deletion of a potential electrostatic interaction in T199A results in very little change in the FFCF, but the insertion of the bulky phenylalanine ring in L198F causes much faster dynamics. We conclude that the fast, sub-picosecond time scale in the correlation function is attributable to hydrogen bond dynamics, and the slow, apparently static contribution is due to the conformational flexibility of Zn-bound azide in the active site.