Crystal structures of substrate and substrate analog complexes of protocatechuate 3,4-dioxygenase: endogenous Fe3+ ligand displacement in response to substrate binding.
Crystal structures of substrate and substrate analog complexes of protocatechuate 3,4-dioxygenase: endogenous Fe3+ ligand displacement in response to substrate binding.
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原儿茶酸 3,4-双加氧酶的底物和底物类似物复合物的晶体结构：响应底物结合的内源 Fe3 配体置换。
DOI：
10.1021/bi970469f
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发表时间：
1997
期刊：
影响因子：
2.9
通讯作者：
Ohlendorf,DH
中科院分区：
文献类型：
--
作者：
Orville,AM;Lipscomb,JD;Ohlendorf,DH
原儿茶酸3，4-双加氧酶（3，4-PCD）利用三价铁离子催化3，4-二羟基苯甲酸酯（PCA）的芳环裂解，通过引入两个双氧原子产生β-羧基-顺式，顺式-粘康酸。厌氧3，4-PCD·PCA复合物、与两种杂环PCA类似物2-羟基异烟酸N-氧化物（INO）和6-羟基烟酸N-氧化物（NNO）的需氧复合物以及3，4-PCD·INO·CN和3，4-PCD·NNO·CN的三元复合物的晶体结构已在2.1−2.2 μ m分辨率下测定，并在0.165和0.184之间进行了R因子修正。PCA、INO和NNO与活性位点Fe 3+形成非常相似的不对称螯合复合物，导致内源性轴向酪氨酸Fe 3+配体Tyr 447（147β）解离。从铁中释放后，Tyr 447通过与Tyr 16（16α）和Asp 413（113β）的氢键结合而稳定，并在PCA的C3−C4键附近形成一个小空腔的顶部。在厌氧的3，4-PCD·PCA复合物中，该空腔中的赤道Fe 3+配位未被占据，但在3，4-PCD·INO和3，4-PCD·NNO复合物中与溶剂分子配位，在3，4-PCD·INO·CN和3，4-PCD·NNO·CN复合物中与CN-配位。这表明O2类似物可以占据空腔，并表明亲电O2对PCA的攻击是从该位点开始的。内源性Tyr 447的解离和铁配位球的扩张是3，4-PCD·底物复合物的新特征，它们在O2攻击底物的激活中起着重要作用。总之，这里和前面的论文[Orville，A. M.，Elango，N.，利普斯科姆，J.D.，& Ohlendorf，D. H.（1997）Biochemistry 36，10039 - 10051]提供了3，4-PCD和相关的含Fe 3+双加氧酶的反应循环中的几个步骤的原子模型。
Protocatechuate 3,4-dioxygenase (3,4-PCD) utilizes a ferric ion to catalyze the aromatic ring cleavage of 3,4-dihydroxybenzoate (PCA) by incorporation of both atoms of dioxygen to yield β-carboxy-cis,cis-muconate. The crystal structures of the anaerobic 3,4-PCD·PCA complex, aerobic complexes with two heterocyclic PCA analogs, 2-hydroxyisonicotinic acidN-oxide (INO) and 6-hydroxynicotinic acidN-oxide (NNO), and ternary complexes of 3,4-PCD·INO·CN and 3,4-PCD·NNO·CN have been determined at 2.1−2.2 Å resolution and refined toR-factors between 0.165 and 0.184. PCA, INO, and NNO form very similar, asymmetrically chelated complexes with the active site Fe3+that result in dissociation of the endogenous axial tyrosinate Fe3+ligand, Tyr447 (147β). After its release from the iron, Tyr447 is stabilized by hydrogen bonding to Tyr16 (16α) and Asp413 (113β) and forms the top of a small cavity adjacent to the C3−C4 bond of PCA. The equatorial Fe3+coordination site within this cavity is unoccupied in the anaerobic 3,4-PCD·PCA complex but coordinates a solvent molecule in the 3,4-PCD·INO and 3,4-PCD·NNO complexes and CN-in the 3,4-PCD·INO·CN and 3,4-PCD·NNO·CN complexes. This shows that an O2analog can occupy the cavity and suggests that electrophilic O2attack on PCA is initiated from this site. Both the dissociation of the endogenous Tyr447 and the expansion of the iron coordination sphere are novel features of the 3,4-PCD·substrate complex which appear to play essential roles in the activation of substrate for O2attack. Together, the structures presented here and in the preceding paper [Orville, A. M., Elango, N., Lipscomb, J. D., & Ohlendorf, D. H. (1997)Biochemistry36, 10039−10051] provide atomic models for several steps in the reaction cycle of 3,4-PCD and related Fe3+-containing dioxygenases.