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      Role of Protein–Protein Interactions in Cytochrome P450-Mediated Drug Metabolism and Toxicity

      review-article
      , ,
      Chemical Research in Toxicology
      American Chemical Society

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          Abstract

          Through their unique oxidative chemistry, cytochrome P450 monooxygenases (CYPs) catalyze the elimination of most drugs and toxins from the human body. Protein–protein interactions play a critical role in this process. Historically, the study of CYP–protein interactions has focused on their electron transfer partners and allosteric mediators, cytochrome P450 reductase and cytochrome b5. However, CYPs can bind other proteins that also affect CYP function. Some examples include the progesterone receptor membrane component 1, damage resistance protein 1, human and bovine serum albumin, and intestinal fatty acid binding protein, in addition to other CYP isoforms. Furthermore, disruption of these interactions can lead to altered paths of metabolism and the production of toxic metabolites. In this review, we summarize the available evidence for CYP protein–protein interactions from the literature and offer a discussion of the potential impact of future studies aimed at characterizing noncanonical protein–protein interactions with CYP enzymes.

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          Most cited references154

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          The many roles of cytochrome b5.

          Four distinct suggestions have been made to explain the mechanism of the cytochrome b(5)-imposed positive modifier action of the cytochrome P450 monooxygenase reaction. The first mechanism involves a direct input of an electron into the monooxygenase cycle. This is the second of the two electrons necessary for activation of molecular oxygen, and appears to be a rate-limiting step in the monooxygenase reaction. P450 monooxygenases all appear to be uncoupled to varying extents, releasing superoxide and hydrogen peroxide instead of oxidized substrate. A second mechanism suggests that cytochrome b(5) acts as a positive modifier of the monooxygenase by decreasing the extent of uncoupling of the monooxygenase reaction. The implication is that a slow input of the second electron allows uncoupling of a superoxide anion instead of formation of two-electron reduced oxygen. Faster input of the second electron via cytochrome b(5) would result in formation of more of the activated oxygen that reacts with substrate to form product. A third suggestion involves formation of a two-hemoprotein complex between cytochrome b(5) and cytochrome P450 that allows acceptance of two electrons from NADPH-cytochrome P450 reductase. Uncomplexed cytochrome P450 accepts an electron from the reductase, dissociates from it, binds oxygen, and re-associates with the reductase to accept another electron. Complexation with cytochrome b(5) enhances the rate of formation of the active oxygen by obviating the need for two interactions with reductase. The fourth mechanism has cytochrome b(5) serving as an effector without a reduction-oxidation role in the monooxygenation reaction. This effector function may be to enhance the breakdown of the oxygenated hemoprotein to products or to facilitate flow of electrons through the system. Copyright 2002 Elsevier Science Inc.
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            Structure of a cytochrome P450-redox partner electron-transfer complex.

            The crystal structure of the complex between the heme- and FMN-binding domains of bacterial cytochrome P450BM-3, a prototype for the complex between eukaryotic microsomal P450s and P450 reductase, has been determined at 2.03 A resolution. The flavodoxin-like flavin domain is positioned at the proximal face of the heme domain with the FMN 4.0 and 18.4 A from the peptide that precedes the heme-binding loop and the heme iron, respectively. The heme-binding peptide represents the most efficient and coupled through-bond electron pathway to the heme iron. Substantial differences between the FMN-binding domains of P450BM-3 and microsomal P450 reductase, observed around the flavin-binding sites, are responsible for different redox properties of the FMN, which, in turn, control electron flow to the P450.
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              Identification of the PGRMC1 protein complex as the putative sigma-2 receptor binding site

              The sigma-2 receptor, whose gene remains to be cloned, has been validated as a biomarker for tumor cell proliferation. Here we report the use of a novel photoaffinity probe, WC-21, to identify the sigma-2 receptor binding site. WC-21, a sigma-2 ligand containing both a photoactive moiety azide and a fluorescein isothiocyanate group, irreversibly labels sigma-2 receptors in rat liver; the membrane-bound protein was then identified as PGRMC1 (progesterone receptor membrane component-1). Immunocytochemistry reveals that both PGRMC1 and SW120, a fluorescent sigma-2 receptor ligand, colocalizes with molecular markers of the endoplasmic reticulum and mitochondria in HeLa cells. Overexpression and knockdown of the PGRMC1 protein results in an increase and a decrease in binding of a sigma-2 selective radioligand, respectively. The identification of the putative sigma-2 receptor binding site as PGRMC1 should stimulate the development of unique imaging agents and cancer therapeutics that target the sigma-2 receptor/PGRMC1 complex.
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                Author and article information

                Journal
                Chem Res Toxicol
                Chem. Res. Toxicol
                tx
                crtoec
                Chemical Research in Toxicology
                American Chemical Society
                0893-228X
                1520-5010
                18 August 2015
                18 August 2014
                15 September 2014
                : 27
                : 9
                : 1474-1486
                Affiliations
                []XenoTech, LLC , 16825 West 116th Street, Lenexa, Kansas 66219, United States
                []Department of Pharmacology, Toxicology, and Therapeutics, The University of Kansas Medical Center , 3901 Rainbow Boulevard, MS-1018, Kansas City, Kansas 66160, United States
                Author notes
                [* ]Tel.: (913) 588-4760; Fax: (913) 588-7501; E-mail: jlampe@ 123456kumc.edu .
                Article
                10.1021/tx500203s
                4164225
                25133307
                7ec21678-c424-482b-836a-ad42696814ef
                Copyright © 2014 American Chemical Society

                Terms of Use

                History
                : 20 May 2014
                Funding
                National Institutes of Health, United States
                Categories
                Review
                Custom metadata
                tx500203s
                tx-2014-00203s

                Toxicology
                Toxicology

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