Structure of the trypanosome cyanide-insensitive alternative oxidase
Structure of the trypanosome cyanide-insensitive alternative oxidase
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DOI：
10.1073/pnas.1218386110
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发表时间：
2013-03-19
影响因子：
11.1
通讯作者：
Kita, Kiyoshi
中科院分区：
文献类型：
--
作者：
Shiba, Tomoo;Kido, Yasutoshi;Kita, Kiyoshi
除了血红素铜氧化酶，所有高等植物、一些藻类、酵母、霉菌、后生动物和病原微生物如布氏锥虫都含有另外的末端氧化酶，氰化物不敏感的交替氧化酶（AOX）。AOX是一种二铁羧酸盐蛋白，其催化泛醇将分子氧还原为水的四电子还原。于T.布氏杆菌是一种引起人类非洲昏睡病的寄生虫，AOX在该寄生虫以其血流形式的存活中起着关键作用。由于AOX在哺乳动物中不存在，因此这种蛋白质代表了独特且有前途的治疗靶点。尽管它的生物能量和医学重要性，然而，任何AOX的结构特征尚未阐明。在这里，我们报告的晶体结构的锥虫交替氧化酶的存在下和存在下的ascofuranone衍生物。所有的结构表明，氧化酶是一个homodimer与nonhaem二铁羧酸活性位点埋在一个四螺旋束。不寻常的是，活性位点仅由四个谷氨酸残基在其氧化的无底物状态下连接;然而，抑制剂结合诱导组氨酸残基的连接。高度保守的Tyr 220位于活性位点的4埃范围内，对催化活性至关重要。所有的结构还揭示了每个单体有两个疏水空腔。两种抑制剂分别在活性位点和Tyr 220的4埃和5埃内结合到一个空腔。第二空腔在二铁中心处与所述通道结合空腔相互作用。我们认为，这两个空腔结合泛醇和沿着与Tyr 220是所需的催化循环O-2还原。
In addition to haem copper oxidases, all higher plants, some algae, yeasts, molds, metazoans, and pathogenic microorganisms such as Trypanosoma brucei contain an additional terminal oxidase, the cyanide-insensitive alternative oxidase (AOX). AOX is a diiron carboxylate protein that catalyzes the four-electron reduction of dioxygen to water by ubiquinol. In T. brucei, a parasite that causes human African sleeping sickness, AOX plays a critical role in the survival of the parasite in its bloodstream form. Because AOX is absent from mammals, this protein represents a unique and promising therapeutic target. Despite its bioenergetic and medical importance, however, structural features of any AOX are yet to be elucidated. Here we report crystal structures of the trypanosomal alternative oxidase in the absence and presence of ascofuranone derivatives. All structures reveal that the oxidase is a homodimer with the nonhaem diiron carboxylate active site buried within a four-helix bundle. Unusually, the active site is ligated solely by four glutamate residues in its oxidized inhibitor-free state; however, inhibitor binding induces the ligation of a histidine residue. A highly conserved Tyr220 iswithin 4 angstrom of the active site and is critical for catalytic activity. All structures also reveal that there are two hydrophobic cavities per monomer. Both inhibitors bind to one cavity within 4 angstrom and 5 angstrom of the active site and Tyr220, respectively. A second cavity interacts with the inhibitor-binding cavity at the diiron center. We suggest that both cavities bind ubiquinol and along with Tyr220 are required for the catalytic cycle for O-2 reduction.