pH-dependent mechanism of nitric oxide release in nitrophorins 2 and 4.
pH-dependent mechanism of nitric oxide release in nitrophorins 2 and 4.
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DOI：
10.1021/jp806906x
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发表时间：
2009-01-29
期刊：
影响因子：
--
通讯作者：
Roitberg AE
中科院分区：
文献类型：
--
作者：
Swails JM;Meng Y;Walker FA;Marti MA;Estrin DA;Roitberg AE
硝普盐蛋白是一氧化氮（NO）载体蛋白，它通过依赖pH的构象变化来运输和释放NO。它们在低pH环境中紧密结合NO，并在高pH环境中释放它。实验证据表明，NO解离平衡常数Kd的增加主要是由于NO释放速率的增加。结构和动力学数据有力地表明，硝普盐蛋白（NPs）通过依赖pH的构象变化调节NO从活性位点向溶剂的迁移来控制NO的逸出。NP2和NP4是该家族中两种具有代表性的蛋白质，总体序列同一性为39%，有趣的是，NP2释放NO的速度比NP4慢。硝普盐蛋白的NO释放主要依赖于NO逸出速率这一观点使得硝普盐蛋白在典型的血红素蛋白中成为一种非常特殊的情况。依赖pH的构象变化与配体释放机制之间的联系尚未完全理解，pH诱导的结构转变的结构基础以及硝普盐蛋白中不同的NO释放模式尚未解决，但这些都是有趣的问题。在这项工作中，我们使用了最先进的分子动力学模拟来研究NP2和NP4在低pH和高pH状态下的NO逸出过程。我们的结果表明，两种硝普盐蛋白都通过在低pH环境下的“关闭”构象和高pH环境下的“开放”构象之间切换来调节NO的释放。在这两种蛋白质中，这种变化是由NP4中的共同残基Asp30和NP2中的Asp29的不同质子化引起的，并且NO逸出途径是保守的。最后，我们的结果表明，在NP2中，向“开放”构象的构象变化比NP4小，这导致NO释放的能垒更高。
Nitrophorins are NO carrier proteins that transport and release NO through a pH dependent conformational change. They bind NO tightly in a low pH environment and release it in a higher pH environment. Experimental evidence shows that the increase in the NO dissociation equilibrium constant, Kd, is due mainly to an increase in the NO release rate. Structural and kinetic data strongly suggest that NPs control NO escape by modulating its migration from the active site to the solvent through a pH dependent conformational change. NP2 and NP4 are two representative proteins of the family displaying a 39% overall sequence identity and, interestingly, NP2 releases NO slower than NP4. The proposal that NPs' NO release relies mainly on the NO escape rate make NPs a very peculiar case among typical heme proteins. The connection between the pH dependent conformational change and ligand release mechanism is not fully understood and the structural basis for the pH induced structural transition and the different NO release patterns in NPs are unresolved, yet interesting issues. In this work we have used state of the art molecular dynamics simulations to study the NO escape process in NP2 and NP4 in both the low and high pH states. Our results show that both NPs modulate NO release by switching between a “closed” conformation in a low pH environment and an “open” conformation at higher pH. In both proteins the change is caused by the differential protonation of a common residue Asp30 in NP4 and Asp29 in NP2, and the NO escape route is conserved. Finally, our results show that in NP2, the conformational change to the “open” conformation is smaller than that for NP4 which results in a higher barrier for NO release.
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影响因子：
2.9
作者：
Andersen, JF;Champagne, DE;Montfort, WR
通讯作者：
Montfort, WR
DOI：
10.1002/bmb.2002.494030010016
发表时间：
2002-01-01
影响因子：
1.4
作者：
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通讯作者：
Montfort, WR
影响因子：
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作者：
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通讯作者：
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影响因子：
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作者：
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通讯作者：
Montfort, WR
影响因子：
15
作者：
Kalko, SG;Gelpí, JL;Orozco, M
通讯作者：
Orozco, M