An engineered heme-copper center in myoglobin: CO migration and binding.
An engineered heme-copper center in myoglobin: CO migration and binding.
复制标题
肌红蛋白中的工程血红素铜中心：CO 迁移和结合
DOI：
10.1016/j.bbapap.2013.02.031
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
Nienhaus
中科院分区：
文献类型：
--
作者：
Nienhaus;Nienhaus
利用傅里叶变换红外光谱和闪光光解研究了CO在CuBMb（一种铜结合肌红蛋白双突变体L29 H-F43 H）中的迁移和结合。该突变体最初是为了模拟血红素铜氧化酶的催化位点而设计的。野生型蛋白Mb和CuBMb的比较表明，在远端口袋中的铜离子引起显着的影响配体结合血红素铁。在Mb和无铜CuBMb中，初级和次级配体对接位点在光解离时是可接近的。在铜结合的CuBMb，配体不迁移到二级对接网站，而是协调的铜离子。从外部进入血红素口袋的配体通常不会被容纳两个额外的大咪唑环的紧密远端口袋有效地捕获。然而，在Cu离子处的结合确保了在CuBMb中的有效捕获。Cu离子还限制了His 64侧链的运动，这是配体运动进入活性位点的入口/出口门，并且这种限制导致增强的成对和缓慢的双分子CO再结合。这些结果支持了目前血红蛋白中配体结合的机制观点和血红素铜氧化酶活性中CuBin的作用。这篇文章是题为“氧结合和传感蛋白”的特刊的一部分。
We have investigated CO migration and binding in CuBMb, a copper-binding myoglobin double mutant (L29H–F43H), by using Fourier transform infrared spectroscopy and flash photolysis over a wide temperature range. This mutant was originally engineered with the aim to mimic the catalytic site of heme–copper oxidases. Comparison of the wild-type protein Mb and CuBMb shows that the copper ion in the distal pocket gives rise to significant effects on ligand binding to the heme iron. In Mb and copper-free CuBMb, primary and secondary ligand docking sites are accessible upon photodissociation. In copper-bound CuBMb, ligands do not migrate to secondary docking sites but rather coordinate to the copper ion. Ligands entering the heme pocket from the outside normally would not be captured efficiently by the tight distal pocket housing the two additional large imidazole rings. Binding at the Cu ion, however, ensures efficient trapping in CuBMb. The Cu ion also restricts the motions of the His64 side chain, which is the entry/exit door for ligand movement into the active site, and this restriction results in enhanced geminate and slow bimolecular CO rebinding. These results support current mechanistic views of ligand binding in hemoglobins and the role of the CuBin the active of heme–copper oxidases. This article is part of a Special Issue entitled: Oxygen Binding and Sensing Proteins.