Adrenodoxin allosterically alters human cytochrome P450 11B enzymes to accelerate substrate binding and decelerate release†

IF 4.2 Q2 BIOCHEMISTRY & MOLECULAR BIOLOGY
Cara L. Loomis, Sang-Choul Im and Emily E. Scott
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引用次数: 0

Abstract

Two human mitochondrial membrane CYP11B enzymes play a pivotal role in steroidogenesis. CYP11B1 generates the major glucocorticoid cortisol, while CYP11B2 catalysis yields the primary mineralocorticoid aldosterone. Catalysis by both requires electron delivery by a soluble iron–sulfur adrenodoxin redox partner. However recent studies have shown that adrenodoxin/CYP11B interaction alone allosterically increases substrate and inhibitor affinity as exhibited by decreased dissociation constant (Kd) values. The current study moves beyond such equilibrium studies, by defining adrenodoxin effects on the rates of P450 ligand binding and release separately. Stopped-flow data clearly demonstrate that adrenodoxin interaction with the P450 proximal surfaces increases ligand binding in both P450 CYP11B active sites by increasing the on rate constant and decreasing the off rate constant. As substrate entry and exit from the sequestered P450 active site requires conformational changes on the distal side of the P450 enzyme, a likely explanation is that adrenodoxin binding allosterically modulates CYP11B conformational changes. The 93% identical CYP11B enzymes can bind and hydroxylate each other's native substrates differing only by a hydroxyl. However, CYP11B1 exhibits monophasic substrate binding and CYP11B2 biphasic substrate binding, even when the substrates are swapped. This indicates that small differences in amino acid sequence between human CYP11B1 and CYP11B2 enzymes are more functionally important in ligand binding and could suggest avenues for more selective inhibition of these drug targets. Both protein/protein interactions and protein/substrate interactions are most likely to act by modulating CYP11B conformational dynamics.

Abstract Image

肾上腺素异生素能改变人类细胞色素 P450 11B 酶,从而加速底物结合并减慢释放速度
人类线粒体膜上的两种 CYP11B 酶在类固醇生成过程中发挥着关键作用。CYP11B1 生成主要的糖皮质激素皮质醇,而 CYP11B2 催化生成主要的矿质皮质激素醛固酮。两者的催化作用都需要可溶性铁硫肾上腺素氧化还原伴侣提供电子。然而,最近的研究表明,肾上腺素多糖/CYP11B 自身的相互作用会通过降低解离常数(Kd)值来增加亚酸盐和抑制剂的亲和力。目前的研究超越了这种平衡研究,分别确定了肾上腺素多辛对 P450 配体结合和释放速率的影响。截流数据清楚地表明,肾上腺素多辛与 P450 近端表面的相互作用增加了 P450 CYP11B 两个活性位点的配体结合率,从而提高了开启率常数,降低了关闭率常数。由于底物进出被封闭的 P450 活性位点需要 P450 酶远端构象的改变,一种可能的解释是肾上腺素多辛的结合异构调节了 CYP11B 的构象变化。93% 相同的 CYP11B 酶可以结合并羟化彼此的原生底物,只是羟基不同而已。然而,即使底物互换,CYP11B1 也表现出单相底物结合,而 CYP11B2 则表现出双相底物结合。这表明,人类 CYP11B1 和 CYP11B2 酶之间氨基酸序列的细微差别在配体结合方面具有更重要的功能,并可能为更有选择性地抑制这些药物靶点提供了途径。蛋白质/蛋白质相互作用和蛋白质/底物相互作用最有可能通过调节 CYP11B 的构象动力学发挥作用。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
CiteScore
6.10
自引率
0.00%
发文量
128
审稿时长
10 weeks
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