Myoglobin-CO substate structures and dynamics: Multidimensional vibrational echoes and molecular dynamics simulations
Myoglobin-CO substate structures and dynamics: Multidimensional vibrational echoes and molecular dynamics simulations
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DOI：
10.1021/ja035654x
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发表时间：
2003-11-12
影响因子：
15
通讯作者：
Fayer, MD
中科院分区：
文献类型：
--
作者：
Merchant, KA;Noid, WG;Fayer, MD
在 300 K 下获得了抹香鲸碳单氧肌红蛋白 (MbCO) 的光谱分辨红外刺激振动回波数据。测得的 CO 配体的相移动力学与通过分子动力学 (MD) 模拟计算的 MbCO 的相移动力学一致，其中残基组氨酸 64 (His64) 具有咪唑 epsilon 氮 质子化（N-ε-H）。 MD 模拟中观察到的两种构象亚态结构 B-epsilon 和 R-epsilon 分别分配给 MbCO 的光谱 A(1) 和 A(3) 构象亚态，基于这些亚态的实验测量和计算的相移动力学之间的一致性。在 A(1) 亚状态中，His64 的 N-epsilon-H 质子和 N-delta 与 CO 配体的距离大约相等，而在 A(3) 亚状态中，His64 的 N-epsilon-H 朝向 CO，N,5 位于蛋白质表面。 MID 模拟表明，His64 的动力学代表了飞秒和皮秒时间尺度上 A3 态 CO 配体振动相移的主要来源。 A(1) 态的相移在飞秒时间尺度上由 His64 控制，在较长时间尺度上由其余蛋白质和水溶剂控制。
Spectrally resolved infrared stimulated vibrational echo data were obtained for sperm whale carbonmonoxymyoglobin (MbCO) at 300 K. The measured dephasing dynamics of the CO ligand are in agreement with dephasing dynamics calculated with molecular dynamics (MD) simulations for MbCO with the residue histidine-64 (His64) having its imidazole epsilon nitrogen protonated (N-epsilon-H). The two conformational substate structures B-epsilon and R-epsilon observed in the MD simulations are assigned to the spectroscopic A(1) and A(3) conformational substates of MbCO, respectively, based on the agreement between the experimentally measured and calculated dephasing dynamics for these substates. In the A(1) substate, the N-epsilon-H proton and N-delta of His64 are approximately equidistant from the CO ligand, while in the A(3) substate, the N-epsilon-H of His64 is oriented toward the CO, and the N,5 is on the surface of the protein. The MID simulations show that dynamics of His64 represent the major source of vibrational dephasing of the CO ligand in the A3 state on both femtosecond and picosecond time scales. Dephasing in the A(1) state is controlled by His64 on femtosecond time scales, and by the rest of the protein and the water solvent on longer time scales.