Two sites of interaction of anions with cytochrome a in oxidized bovine cytochrome c oxidase.
Two sites of interaction of anions with cytochrome a in oxidized bovine cytochrome c oxidase.
复制标题
氧化牛细胞色素 c 氧化酶中阴离子与细胞色素 a 相互作用的两个位点。
DOI：
10.1074/jbc.m311834200
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发表时间：
2004
期刊：
影响因子：
--
通讯作者：
Palmer,Graham
中科院分区：
文献类型：
--
作者：
Fabian,Marian;Jancura,Daniel;Palmer,Graham
用EPR谱研究了细胞色素氧化酶（CcO）与阴离子的相互作用。影响细胞色素EPR g = 3信号的阴离子可分为两类。一组由卤化物（Cl-，Br-和I-）组成，并诱导g = 3信号的高场位移。含氮阴离子（CN-、NO2-、N3-、NO3-）在第二组中并且使g = 3信号向低场移动。CcO的EPR谱中的位移与配体与双核中心的结合无关。详细描述了每组中一个代表性化合物（叠氮化物和氯化物）的结合特性。的依赖性的变化对氯离子浓度是一致的，与一个单一的结合位点在分离的氧化酶与aKdof <$3毫米。在线粒体中，appartKdwas被发现是约4倍大于分离的酶。数据表明，它是氯阴离子，是结合到CcO，有一个亲水性的大小选择性的访问通道，该网站从线粒体膜的胞质侧。观察到的叠氮化物和氯化物之间的竞争被解释为叠氮化物结合到三个网站：两个是明显的X-射线结构加上氯化物结合位点。这表明Mg~（2+）或Arg-438/Arg-439是氯离子结合位点，并提出了配体诱导g = 3信号移位的机制。
An interaction between cytochromeain oxidized cytochromecoxidase (CcO) and anions has been characterized by EPR spectroscopy. Those anions that affect the EPR g = 3 signal of cytochromeacan be divided into two groups. One group consists of halides (Cl-, Br-, and I-) and induces an upfield shift of the g = 3 signal. Nitrogen-containing anions (CN-, NO2-, N3-, NO3-) are in the second group and shift the g = 3 signal downfield. The shifts in the EPR spectrum of CcO are unrelated to ligand binding to the binuclear center. The binding properties of one representative from each group, azide and chloride, were characterized in detail. The dependence of the shift on chloride concentration is consistent with a single binding site in the isolated oxidized enzyme with aKdof ∼3 mm. In mitochondria, the apparentKdwas found to be about four times larger than that of the isolated enzyme. The data indicate it is the chloride anion that is bound to CcO, and there is a hydrophilic size-selective access channel to this site from the cytosolic side of the mitochondrial membrane. An observed competition between azide and chloride is interpreted by azide binding to three sites: two that are apparent in the x-ray structure plus the chloride-binding site. It is suggested that either Mg2+or Arg-438/Arg-439 is the chloride-binding site, and a mechanism for the ligand-induced shift of the g = 3 signal is proposed.