Auchus R J, Worthy K, Geller D H, Miller W L
Department of Internal Medicine, UT Southwestern Medical Center, Dallas, TX 75390-8857, USA.
Endocr Res. 2000 Nov;26(4):695-703. doi: 10.3109/07435800009048589.
Human P450c17 performs at least six chemical transformations, but this spectrum of activity is differentially regulated by structural changes and by redox partner proteins. Furthermore, P450c17 isoforms from different species with approximately 90% amino acid identity exhibit markedly different relative rates for these transformations. Although this phenomenology has been recognized for nearly 20 years, the underlying chemistry and structural basis for these effects are poorly understood. We have constructed a structural model of human P450c17 using computational chemistry to understand informative, naturally occurring human mutations and to provide a rational basis for designing alterations in P450c17 that probe functional domains of the protein. We have mapped with considerable confidence key residues involved in the interaction with redox partner proteins, including K89, R347, and R358, which form positive charges on the "proximal" surface of P450c17. Neutralization of these charges selectively impairs 17, 20-lyase activity without large reductions in 17alpha-hydroxylase activity or 17alpha-hydroxypregnenolone binding. We are now directing our efforts to the identification of key residues in the active site that mediate the substrate specificity and catalytic selectivity of human P450c17.
人类细胞色素P450c17可催化至少六种化学转化反应，但其活性谱受到结构变化和氧化还原伴侣蛋白的差异调节。此外，不同物种中氨基酸序列一致性约为90%的P450c17同工酶对这些转化反应的相对速率表现出显著差异。尽管这一现象已被认识近20年，但对于这些效应背后的化学和结构基础仍知之甚少。我们利用计算化学构建了人类P450c17的结构模型，以了解有意义的天然人类突变，并为设计P450c17的改变提供合理依据，从而探究该蛋白的功能域。我们已经相当有把握地确定了与氧化还原伴侣蛋白相互作用的关键残基，包括K89、R347和R358，它们在P450c17的“近端”表面形成正电荷。中和这些电荷会选择性地损害17,20-裂解酶活性，而不会大幅降低17α-羟化酶活性或17α-羟基孕烯醇酮结合能力。我们目前正致力于确定活性位点中的关键残基，这些残基介导了人类P450c17的底物特异性和催化选择性。
