亚基相互作用改变了对甲酚甲基羟化酶中的血红素活性位点几何结构。
Subunit interactions change the heme active-site geometry in p-cresol methylhydroxylase.
作者信息
McLendon G L, Bagby S, Charman J A, Driscoll P C, McIntire W S, Mathews F S, Hill H A
机构信息
Department of Chemistry, University of Rochester, NY 14627.
出版信息
Proc Natl Acad Sci U S A. 1991 Nov 1;88(21):9463-7. doi: 10.1073/pnas.88.21.9463.
The enzyme p-cresol methylhydroxylase [4-cresol: (acceptor) oxidoreductase (methyl-hydroxylating), EC 1.17.99.1] contains two subunits: a cytochrome c (electron transfer) subunit (cytochrome cpc) and a flavin (catalytic) subunit. When these subunits are separated by isoelectric focusing, a stable cytochrome subunit is obtained. Significant differences are observed between the one-dimensional NMR spectra of oxidized cytochrome cpc and of oxidized p-cresol methylhydroxylase. Analysis of the two-dimensional nuclear Overhauser enhancement and exchange spectroscopy (NOESY) spectrum of reduced cytochrome cpc suggests that the axial ligand, Met-50, of the stable subunit reorients by a rotation about the C gamma-S delta bond when cytochrome cpc binds to the flavin subunit. This reorientation must result in a change in bonding at the heme, which is reflected both in the para-magnetically shifted resonances and in the redox potential. p-Cresol methylhydroxylase thereby provides an interesting example of the coupling of subunit interactions to active-site structure and reactivity.
对甲酚甲基羟化酶[4-甲酚：（受体）氧化还原酶（甲基羟化），EC 1.17.99.1]包含两个亚基：一个细胞色素c（电子传递）亚基（细胞色素cpc）和一个黄素（催化）亚基。当这些亚基通过等电聚焦分离时，可得到一个稳定的细胞色素亚基。在氧化型细胞色素cpc和氧化型对甲酚甲基羟化酶的一维核磁共振谱之间观察到显著差异。对还原型细胞色素cpc的二维核Overhauser增强和交换光谱（NOESY）谱的分析表明，当细胞色素cpc与黄素亚基结合时，稳定亚基的轴向配体Met-50会围绕Cγ-Sδ键旋转而重新定向。这种重新定向必然导致血红素处键合的变化，这在顺磁位移共振和氧化还原电位中都有所体现。对甲酚甲基羟化酶因此提供了一个亚基相互作用与活性位点结构和反应性耦合的有趣例子。
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