亚洲象（Elephas maximus）肌红蛋白的结构-动力学-功能关系。关于功能重要运动的光谱学和闪光光解研究。
Structure-dynamics-function relationships in Asian elephant (Elephas maximus) myoglobin. An optical spectroscopy and flash photolysis study on functionally important motions.
作者信息
Cupane A, Leone M, Vitrano E, Cordone L, Hiltpold U R, Winterhalter K H, Yu W, Di Iorio E E
机构信息
Istituto di Fisica, Università di Palermo, Italy.
出版信息
Biophys J. 1993 Dec;65(6):2461-72. doi: 10.1016/S0006-3495(93)81311-0.
In this work we report the thermal behavior (10-300 K) of the Soret band lineshape of deoxy and carbonmonoxy derivatives of Asian elephant (Elephas maximus) and horse myoglobins together with their carbon monoxide recombination kinetics after flash photolysis; the results are compared to analogous data relative to sperm whale myoglobin. The Soret band profile is modeled as a Voigt function that accounts for the coupling with high and low frequency vibrational modes, while inhomogeneous broadening is taken into account with suitable distributions of purely electronic transition frequencies. This analysis makes it possible to isolate the various contributions to the overall lineshape that; in turn, give information on structural and dynamic properties of the systems studied. The optical spectroscopy data point out sizable differences between elephant myoglobin on one hand and horse and sperm whale myoglobins on the other. These differences, more pronounced in deoxy derivatives, involve both the structure and dynamics of the heme pocket; in particular, elephant myoglobin appears to be characterized by larger anharmonic contributions to soft modes than the other two proteins. Flash photolysis data are analyzed as sums of kinetic processes with temperature-dependent fractional amplitudes, characterized by discrete pre-exponentials and either discrete or distributed activation enthalpies. In the whole temperature range investigated the behavior of elephant myoglobin appears to be more complex than that of horse and sperm whale myoglobins, which is in agreement with the increased anharmonic contributions to soft modes found in the former protein. Thus, to satisfactorily fit the time courses for CO recombination to elephant myoglobin five distinct processes are needed, only one of which is populated over the whole temperature range investigated. The remarkable convergence and complementarity between optical spectroscopy and flash photolysis data confirms the utility of combining these two experimental techniques in order to gain new and deeper insights into the functional relevance of protein fluctuations.
在这项工作中，我们报告了亚洲象（Elephas maximus）和马肌红蛋白的脱氧和一氧化碳衍生物的索雷特带线形的热行为（10 - 300 K），以及它们在闪光光解后的一氧化碳重组动力学；将结果与抹香鲸肌红蛋白的类似数据进行了比较。索雷特带轮廓被建模为一个考虑了与高频和低频振动模式耦合的洛伦兹函数（Voigt function），同时通过纯电子跃迁频率的合适分布来考虑非均匀展宽。这种分析使得能够分离出对整体线形的各种贡献，进而提供有关所研究系统的结构和动力学性质的信息。光谱数据表明，一方面大象肌红蛋白与另一方面马和抹香鲸肌红蛋白之间存在显著差异。这些差异在脱氧衍生物中更为明显，涉及血红素口袋（heme pocket）的结构和动力学；特别是大象肌红蛋白似乎比其他两种蛋白质对软模式具有更大的非谐贡献。闪光光解数据被分析为具有温度依赖性分数振幅（fractional amplitudes）的动力学过程之和，其特征在于离散的指数前因子和离散或分布的活化焓（activation enthalpies）值）。在所研究的整个温度范围内大象肌红蛋白表现出比马和抹香鲸肌红蛋白更复杂的行为，这与在前一种蛋白质中发现对软模式增加的非谐贡献相一致。因此，为了令人满意地拟合一氧化碳与大象肌红蛋白重组的时间进程，需要五个不同过程；其中只有一个在整个研究温度范围内存在。光谱学和闪光光解数据之间显著的趋同和互补性证实了结合这两种实验技术以获得对蛋白质波动功能相关性的新的和更深入见解的实用性。
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