Tracking protein-protein interactions by NMR: conformational selection in human steroidogenic cytochrome P450 CYP17A1 induced by cytochrome .

The human steroidogenic cytochrome P450 CYP17A1 catalyzes two types of reactions in the biosynthetic pathway leading from pregnenolone to testosterone and several other steroid hormones. The first is the hydroxylation of pregnenolone or progesterone to the corresponding 17α-hydroxy steroid, followed by a lyase reaction that converts these 17α-hydroxy intermediates to the androgens dehydroepiandrosterone and androstenedione, respectively. cytochrome (cyt) is known to act as both an effector and electron donor for the lyase oxidations, markedly stimulating the rate of the lyase reaction in its presence relative to the rate in its absence.

Selective steroidogenic cytochrome P450 haem iron ligation by steroid-derived isonitriles.

Alkyl isonitriles, R-NC, have previously been shown to ligate the heme (haem) iron of cytochromes P450 in both accessible oxidation states (ferrous, Fe, and ferric, Fe). Herein, the preparation of four steroid-derived isonitriles and their interactions with several P450s, including the steroidogenic CYP17A1 and CYP106A2, as well as the more promiscuous drug metabolizers CYP3A4 and CYP2D6, is described. It was found that successful ligation of the heme iron by the isonitrile functionality for a given P450 depends on both the position and stereochemistry of the isonitrile on the steroid skeleton.

Conformational heterogeneity suggests multiple substrate binding modes in CYP106A2.

CYP106A2 (cytochrome P450) is a bacterial enzyme originally isolated from B. megaterium, and has been shown to hydroxylate a wide variety of substrates, including steroids. The regio- and stereochemistry of CYP106A2 hydroxylation has been shown to be dependent on a variety of factors, and hydroxylation often occurs at more than one site and/or with lack of stereospecificity for some substrates.

Hydroxylation Regiochemistry Is Robust to Active Site Mutations in Cytochrome P450 (CYP101A1).

Cytochrome P450 (CYP101A1) catalyzes the hydroxylation of d-camphor by molecular oxygen. The enzyme-catalyzed hydroxylation exhibits a high degree of regioselectivity and stereoselectivity, with a single major product, d-5--hydroxycamphor, suggesting that the substrate is oriented to facilitate this specificity. In previous work, we used an elastic network model and perturbation response scanning to show that normal deformation modes of the enzyme structure are highly responsive not only to the presence of a substrate but also to the substrate orientation.

A dynamic understanding of cytochrome P450 structure and function through solution NMR.

Many economically important biosyntheses incorporate regiospecific and stereospecific oxidations at unactivated carbons. Such oxidations are commonly catalyzed by cytochrome P450 monooxygenases, heme-containing enzymes that activate molecular oxygen while selectively binding and orienting the substrate for reaction. Despite the plethora of P450-catalyzed reactions, the P450 fold is highly conserved, and static structures are often insufficient for characterizing conformational states that contribute to specificity.