晶体的比较锰,iron-dependent homoprotocatechuate 2, 3-dioxygenases。
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审查兆瓦,Wackett LP L小,以至于JD,黑轮DH
晶体的比较锰,iron-dependent homoprotocatechuate 2, 3-dioxygenases。
J Bacteriol。2004年4月,186 (7):1945 - 58。
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15028678 (在PubMed]
- 文摘
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x射线晶体结构homoprotocatechuate 2, 3-dioxygenases隔绝节细菌属globiformis和枯草芽孢fuscum已经决心高分辨率。这些酶表现出83%的序列的身份,但他们的活动取决于不同的过渡金属,分别Mn2 +和价。使金属离子选择性的起源和结构方面的详细分子机制研究。homotetrameric酶属于的类型我家人extradiol加双氧酶(附近的氧螯合总科);每个单体都有四个betaalphabetabetabeta模块形成两个结构同源的氨基端和c端筒状的域。活性部位金属位于c端桶和由两个赤道配体的结扎,H214NE1 E267OE1;一个轴向配体,H155NE1;和两三个水分子。第一次和第二次协调领域的这些酶几乎是相同的(均方根差所有原子,0.19),这表明金属选择性必须变化很大的距离金属和/或改变发生在折叠。衬底(2,3-dihydroxyphenylacetate [HPCA])螯合物的金属不对称地在两个网站反式异吡唑配体与一个独特的交互,移动c端循环。 The loop closes over the bound substrate, presumably to seal the active site as the oxygen activation process commences. An "open" coordination site trans to E267 is the likely binding site for O2. The geometry of the enzyme-substrate complexes suggests that if a transiently formed metal-superoxide complex attacks the substrate without dissociation from the metal, it must do so at the C-3 position. Second-sphere active-site residues that are positioned to interact with the HPCA and/or bound O2 during catalysis are identified and discussed in the context of current mechanistic hypotheses.