Ultrafast dynamics of diatomic ligand binding to nitrophorin 4.
Ultrafast dynamics of diatomic ligand binding to nitrophorin 4.
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DOI：
10.1021/ja910005b
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发表时间：
2010-03-03
影响因子：
15
通讯作者：
Champion, Paul M.
中科院分区：
文献类型：
--
作者：
Benabbas, Abdelkrim;Ye, Xiong;Kubo, Minoru;Zhang, Zhenyu;Maes, Estelle M.;Montfort, William R.;Champion, Paul M.
Nitrophorin 4（NP 4）是一种血红素蛋白，其通过pH敏感的构象变化来储存和递送一氧化氮（NO）。这种蛋白质使用的铁状态的一个高度皱褶血红素紧密结合NO在低pH值和释放它在高pH值。在这项工作中，NO和CO的NP 4的再结合动力学研究作为铁的氧化态和环境的酸度的函数。在pH 5和pH 7时，NO与亚铁NP 4的成对重组过程由单个~7 ps动力学阶段主导，我们将其归因于NO直接从远端口袋重新结合。缺乏pH依赖性部分解释了为什么NP 4不能使用亚铁态来实现其功能。铁NP 4 NO的动力学响应显示两个不同的阶段。随着pH值从5升高到8，较慢阶段的相对双生振幅急剧增加。我们分配的快速相NO再结合的铁蛋白与一个封闭的疏水口袋的构象。慢相被分配给蛋白质在一个开放的构象与更亲水血红素口袋环境。超快动力学分析发现NO的平衡解离速率与开放状态的种群以及从开放口袋逃逸的pH依赖性幅度成比例。当考虑这两个因素时，当pH从5变化到8时，解离速率增加超过一个数量级。观察到CO与亚铁NP 4的重组具有很大的非指数成对振幅，在pH 5时的再结合时间尺度为~10−11-10−9 s，在pH 7时为~10− 10-10−8 s。在pH 5和pH 7的非指数CO再结合动力学占使用一个简单的模型，已被证明是有效的理解CO结合在各种其他血红素系统。
Nitrophorin 4 (NP4) is a heme protein that stores and delivers nitric oxide (NO) through pH sensitive conformational change. This protein uses the ferric state of a highly ruffled heme to bind NO tightly at low pH and release it at high pH. In this work, the rebinding kinetics of NO and CO to NP4 are investigated as a function of iron oxidation state and the acidity of the environment. The geminate recombination process of NO to ferrous NP4 at both pH 5 and pH 7 is dominated by a single ~7 ps kinetic phase that we attribute to the rebinding of NO directly from the distal pocket. The lack of pH dependence explains in part why NP4 cannot use the ferrous state to fulfill its function. The kinetic response of ferric NP4NO shows two distinct phases. The relative geminate amplitude of the slower phase increases dramatically as the pH is raised from 5 to 8. We assign the fast phase of NO rebinding to a conformation of the ferric protein with a closed hydrophobic pocket. The slow phase is assigned to the protein in an open conformation with a more hydrophilic heme pocket environment. Analysis of the ultrafast kinetics finds the equilibrium off-rate of NO to be proportional to the open state population as well as the pH-dependent amplitude of escape from the open pocket. When both factors are considered, the off-rate increases by more than an order of magnitude as the pH changes from 5 to 8. The recombination of CO to ferrous NP4 is observed to have a large non-exponential geminate amplitude with rebinding timescales of ~10−11–10−9 s at pH 5 and ~10−10–10−8 s at pH 7. The non-exponential CO rebinding kinetics at both pH 5 and pH 7 are accounted for using a simple model that has proven effective for understanding CO binding in a variety of other heme systems.
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影响因子：
2.9
作者：
Andersen, JF;Champagne, DE;Montfort, WR
通讯作者：
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作者：
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