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首页> 外文期刊>Biochemistry >Mutation of alpha Phe55 of methylamine dehydrogenase alters the reorganization energy and electronic coupling for its electron transfer reaction with amicyanin
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Mutation of alpha Phe55 of methylamine dehydrogenase alters the reorganization energy and electronic coupling for its electron transfer reaction with amicyanin

机译：甲胺脱氢酶αPHE55的突变改变了与氨酸素电子转移反应的重组能量和电子耦合

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摘要

Methylamine dehydrogenase (MADH) possesses an alpha(2)beta(2) structure with each smaller beta subunit possessing a tryptophan tryptophylquinone (TTQ) prosthetic group. Phe55 of the alpha subunit is located where the substrate channel from the enzyme surface opens into the active site. Site-directed mutagenesis of alphaPhe55 has revealed roles for this residue in determining substrate specificity and binding monovalent cations at the active site. It is now shown that the alphaF55A mutation also increases the rate of the true electron transfer (ET) reaction from O-quinol MADH to amicyanin. The reorganization energy associated with the ET reaction is decreased from 2.3 to 1.8 eV. The electronic coupling associated with the ET reaction is decreased from 12 to 3 cm(-1). The crystal structure of alphaF55A MADH in complex with its electron acceptors, amicyanin and cytochrome c-55li, has been determined. Little difference in the overall structure is seen, relative to the native complex; however, there are significant changes in the solvent content of the active site and substrate channel. The crystal structure of alphaF55A MADH has also been determined with phenylhydrazine covalently bound to TTQ in the active site. Phenylhydrazine binding significantly perturbs the orientation of the TTQ rings relative to each other. The ET results are discussed in the context of the new and old crystal structures of the native and mutant enzymes. [References: 42]
机译：甲胺脱氢酶（MADH）具有α（2）β（2）结构，每个较小的β亚基具有色氨酸色氨酸（TTQ）假体。 α亚基的PHE55位于来自酶表面的基材通道打开活性位点。 ALPHAPHE55的诱变诱变揭示了该残余物在测定活性位点的底物特异性和结合单价阳离子时的作用。现在表明，α55A突变还会增加来自O-Quinol Madh至amicyanin的真正电子转移（ET）反应的速率。与ET反应相关的重组能量从2.3降至1.8eV降低。与ET反应相关的电子耦合从12-3cm（-1）降低。已经确定了alphaf55a madh与其电子受体，amicyanin和细胞色素c-55li的晶体结构已经确定。相对于天然综合体，可以看到整体结构的差异很小;然而，活性部位和衬底通道的溶剂含量存在显着变化。 Alphaf55a Madh的晶体结构也被活性位点中与TTQ共价结合的苯肼确定。苯二肼结合显着渗透到彼此相对于TTQ环的取向。在本地和突变酶的新晶体结构的背景下讨论了ET结果。 [参考：42]

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