Structure of the terminal oxygenase component of angular dioxygenase, carbazole 1,9a-dioxygenase
Structure of the terminal oxygenase component of angular dioxygenase, carbazole 1,9a-dioxygenase
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DOI：
10.1016/j.jmb.2005.05.059
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发表时间：
2005-08-12
影响因子：
5.6
通讯作者：
Omori, T
中科院分区：
文献类型：
--
作者：
Nojiri, H;Ashikawa, Y;Omori, T
咔唑1,9a-双加氧酶（CARDO）通过角位置（C9a）碳与亚氮及其相邻的C1碳的键合催化咔唑的二羟基化。该反应是不同菌株对咔唑降解途径的初始降解反应。只有有限数量的Rieske非血红素铁加氧酶系统（ROSs）可以催化这种称为角双氧合的新反应。角双氧作用也参与了咔唑类化合物的降解途径。化合物、二恶英和CARDO可以催化二恶英的角双氧作用。CARDO由末端加氧酶组分（CARDO- o）和电子传递组分铁氧还蛋白（CARDO- f）和铁氧还蛋白还原酶（CARDO- r）组成。CARDO- o具有同型三聚体结构，这决定了CARDO的底物特异性。在这里，我们以1.95埃的分辨率确定了Janthinobacterium sp.菌株J3的CARDO-O晶体结构。CARDO-O分子的α 3三聚体整体结构大致对应于ROSs其他末端加氧酶组分具有α (3) β(3)构型的a3部分结构。CARDO-O结构是具有α(3)构型的ROSs末端加氧酶组分的第一个例子，并揭示了与邻近亚基相互作用的特定环的存在，这被认为是没有结构β亚基的稳定α(3)相互作用所必不可少的。CARDO-O的底物结合袋的形状与参与萘和联苯降解途径的其他加氧酶组分明显不同。对接模拟表明，咔唑以一种适合于催化角双氧作用的方式与底物结合袋结合。(c) 2005 Elsevier Ltd版权所有。
Carbazole 1,9a-dioxygenase (CARDO) catalyzes the dihydroxylation of carbazole by angular position (C9a) carbon bonding to the imino nitrogen and its adjacent C1 carbon. This reaction is an initial degradation reaction of the carbazole degradation pathway by various bacterial strains. Only a limited number of Rieske non-heme iron oxygenase systems, (ROSs) can catalyze this novel reaction, termed angular dioxygenation. Angular dioxygenation is also involved in the degradation pathways of carbazole-related. compounds, dioxin, and CARDO can catalyze the angular dioxygenation for dioxin. CARDO consists of a terminal oxygenase component (CARDO-O), and the electron transport components, ferredoxin (CARDO-F) and ferredoxin reductase (CARDO-R). CARDO-O has a homotrimeric structure, and governs the substrate specificity of CARDO. Here, we have determined the crystal structure of CARDO-O of Janthinobacterium sp. strain J3 at a resolution of 1.95 angstrom. The alpha 3 trimeric overall structure of the CARDO-O molecule roughly corresponds to the a3 partial structures of other terminal oxygenase components of ROSs that have the alpha(3)beta(3) configuration. The CARDO-O structure is a first example of the terminal oxygenase components of ROSs that have the alpha(3) configuration, and revealed the presence of the specific loops that interact with a neighboring subunit, which is proposed to be indispensable for stable alpha(3) interactions without structural beta subunits. The shape of the substrate-binding pocket of CARDO-O is markedly different from those of other oxygenase components involved in naphthalene and biphenyl degradation pathways. Docking simulations suggested that carbazole binds to the substrate-binding pocket in a manner suitable for catalysis of angular dioxygenation. (c) 2005 Elsevier Ltd. All rights reserved.