STRUCTURE FUNCTION OF CYTOCHROME P450

细胞色素P450氧化多种异源和内源性 化合物。生化、生物物理和计算方法是 应用于检查结构与功能之间的关系 P450与底物、膜脂和微粒体的相互作用 蛋白质。用CO结合动力学作为P450的探针 构象和动力学，以定义各种药物和 P450上的致癌物。特别令人感兴趣的是，这两项发现 人类代谢致癌物的P450 1A1和P450 3A4 代谢的多种重要药物，都是由多个 具有不同底物特异性的构象。这一发现被用来 7，8-萘黄酮对P450 3A4的激活和抑制作用 以及奎尼丁抑制P450 3A4的作用机制 介导的硝苯地平代谢。此外，CO的结合动力学是 应用于检测红霉素与大鼠P450的差异结合 3A1和3A2，其序列相似性为89%。结果表明， 红霉素形成的P450底物结合部位模型 P450 3A1比P450 3A2刚性更强的复合体。这些结果表明 CO结合动力学可以区分紧密相关的P450 同样的微粒体膜。 我们采用分子模拟方法建立了P450 2B1模型。P450 预测了NADPH细胞色素P450还原酶的识别表面， 并制备了相应的多肽并对其进行了评价 抑制P450-还原酶相互作用的能力。最具威力的 多肽抑制剂在拓扑上是从空间上邻近的 C-螺旋、L-螺旋和曲流区的P450序列。模型 还建议了由氨基组成的膜结合结构域 终端区、A前螺旋区和F-G环。此外, 当几个已知的底物对接到底物结合中时 ，观察到的底物与P450的相互作用与 已知的底物特异性的P450 2B1。因此，这个模型表明 该P450的还原酶、膜和底物结合区。

The cytochrome P450s oxidize a wide variety of xenobiotic and endogenous compounds. Biochemical, biophysical and computational approaches were applied to examine the structure-function relationships which govern the interactions of P450s with substrates, membrane lipids and microsomal proteins. The CO binding kinetics was used as a probe of P450 conformation and dynamics, to define the effect of various drugs and carcinogens on P450s. Of particular interest is the finding that both human P450 1A1, which metabolizes carcinogens, and P450 3A4, which metabolizes a variety of important drugs, are composed of multiple conformers with distinct substrate specificities. This finding was used to elucidate 7,8-naphthoflavone activation of P450 3A4 and inhibition of P450 1A1, and the mechanism of quinidine inhibition of P450 3A4 mediated nifedipine metabolism. In addition, CO binding kinetics was applied to examine the differential binding of erythromycin to rat P450s 3A1 and 3A2, which exhibit 89% sequence similarity. The results indicate a model of the P450 substrate binding site in which erythromycin forms a more rigid complex with P450 3A1 than P450 3A2. These results show that CO binding kinetics can distinguish among closely related P450s in the same microsomal membrane. We employed molecular modeling to generate a P450 2B1 model. P450 recognition surfaces for NADPH cytochrome P450 reductase were predicted, and the corresponding peptides were prepared and assessed for their ability to inhibit the P450-reductase interaction. The most potent peptide inhibitors were topographically derived from spatially proximate P450 sequences in the C and L-helices and the meander region. The model also suggests a membrane binding domain which consists of the amino terminal region, the pre-A helix region and the F-G loop. In addition, when several known substrates were docked into the substrate binding site, the observed substrate-P450 interactions were consistent with the known substrate specificity of P450 2B1. This model thus suggests reductase, membrane and substrate binding domains of this P450.