An oxidized tryptophan facilitates copper binding in Methylococcus capsulatus-secreted protein MopE
An oxidized tryptophan facilitates copper binding in Methylococcus capsulatus-secreted protein MopE
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DOI：
10.1074/jbc.m800340200
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发表时间：
2008-05-16
影响因子：
4.8
通讯作者：
Jensen, Harald B.
中科院分区：
文献类型：
--
作者：
Helland, Ronny;Fjellbirkeland, Anne;Jensen, Harald B.
蛋白质可以通过主链氨基和羰基将金属离子与内源性氮氧配体配位，但氨基酸侧链的配位金属不包括色氨酸。在这里，我们首次表明色氨酸代谢产物犬尿氨酸参与蛋白质金属结合位点。甲烷氧化性荚膜甲基球菌（Methylococcus capsulatus, Bath） 1.35埃的MopE*晶体结构提供了其结构和单核铜结合位点的详细信息。MopE*含有一种新的蛋白质折叠，其中只有三分之一的结构与其他已知折叠相似。铜离子周围的几何形状是一个扭曲的四面体，其中一个氧原子来自一个水分子，两个组氨酸咪唑（His-132和His-203），在第四个扭曲的四面体位置是犬尿氨酸（Trp-130的氧化产物）的N1原子。在大肠杆菌中异种表达的MopE*中，Trp-130不被氧化为犬尿氨酸，也不与铜结合。我们的研究结果表明，色氨酸修饰成犬尿氨酸并参与铜的结合是荚膜芽孢杆菌MopE*的先天特性。
Proteins can coordinate metal ions with endogenous nitrogen and oxygen ligands through backbone amino and carbonyl groups, but the amino acid side chains coordinating metals do not include tryptophan. Here we show for the first time the involvement of the tryptophan metabolite kynurenine in a protein metal-binding site. The crystal structure to 1.35 angstrom of MopE* from the methane-oxidizing Methylococcus capsulatus (Bath) provided detailed information about its structure and mononuclear copper-binding site. MopE* contains a novel protein fold of which only one-third of the structure displays similarities to other known folds. The geometry around the copper ion is distorted tetrahedral with one oxygen ligand from a water molecule, two histidine imidazoles (His-132 and His-203), and at the fourth distorted tetrahedral position, the N1 atom of the kynurenine, an oxidation product of Trp-130. Trp-130 was not oxidized to kynurenine in MopE* heterologously expressed in Escherichia coli, nor did this protein bind copper. Our findings indicate that the modification of tryptophan to kynurenine and its involvement in copper binding is an innate property of M. capsulatus MopE*.