Vibrational energy relaxation of "tailored" hemes in myoglobin following ligand photolysis supports energy funneling mechanism of heme "cooling"
Vibrational energy relaxation of "tailored" hemes in myoglobin following ligand photolysis supports energy funneling mechanism of heme "cooling"
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DOI：
10.1021/jp034558f
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发表时间：
2003-09-25
影响因子：
3.3
通讯作者：
Straub, JE
中科院分区：
文献类型：
--
作者：
Bu, LT;Straub, JE
在先前的分子动力学模拟研究中，发现溶剂化碳单氧肌红蛋白中的光解血红素的动能弛豫是单指数衰减过程，弛豫时间常数为5.9 ps [Sagnella，D. E.的;斯特劳布，J.E. J. Phys. Chem. B 2001，105，7057]。强的静电相互作用的异丙酸酯侧链和溶剂化的水分子被证明是唯一的最重要的“门道”的多余的动能耗散的血红素。在这项工作中，血红素“冷却”的分子动力学模拟研究的结果在两个修改的肌红蛋白，其中（1）在血红素的两个异丙酸侧链被氢取代或（2）近端组氨酸被甘氨酸，His 93 Gly取代，提出。对于每一个“定制”的蛋白质，血红素的过剩动能的松弛被发现是一个单一的指数衰减过程。对于His 93 Gly突变体蛋白，弛豫时间被发现是5.9 ps，与天然野生型肌红蛋白的弛豫时间一致。对于肌红蛋白与修改血红素缺乏异丙酸侧链，弛豫时间被发现是8.8 ps-减少了50%相比，为天然肌红蛋白。这些结果提供了强有力的支持的建议，即在天然肌红蛋白的血红素的快速动能松弛的主要通道是直接的能量“funerals”通过血红素侧链周围的溶剂。
In a previous molecular dynamics simulation study, the kinetic energy relaxation of photolyzed heme in solvated carbonmonoxymyoglobin was found to be a single exponential decay process with the relaxation time constant 5.9 ps [Sagnella, D. E.; Straub, J. E. J. Phys. Chem. B 2001, 105, 7057]. The strong electrostatic interaction of the isopropionate side chains and the solvating water molecules was shown to be the single most important "doorway" for dissipation of excess kinetic energy in the heme. In this work, the results of a molecular dynamics simulation study of heme "cooling" in two modified myoglobins, in which (1) the two isopropionate side chains in the heme are replaced by hydrogen or (2) the proximal histidine is replaced by glycine, His93Gly, are presented. For each "tailored" protein, the relaxation of the heme's excess kinetic energy is found to be a single exponential decay process. For the His93Gly mutant protein, the relaxation time is found to be 5.9 ps, in agreement with the relaxation time in native wild-type myoglobin. For myoglobin with the modified heme lacking isopropionate side chains, the relaxation time was found to be 8.8 ps-a decrease by 50% compared to that for native myoglobin. These results lend strong support to the proposal that the predominant channel for fast kinetic energy relaxation of the heme in native myoglobin is directed energy "funneling" through the heme side chains to the surrounding solvent.