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Liu XR, Zhang MM, Gross ML. Mass Spectrometry-Based Protein Footprinting for Higher-Order Structure Analysis: Fundamentals and Applications. Chem Rev 2020; 120:4355-4454. [PMID: 32319757 PMCID: PMC7531764 DOI: 10.1021/acs.chemrev.9b00815] [Citation(s) in RCA: 130] [Impact Index Per Article: 32.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Proteins adopt different higher-order structures (HOS) to enable their unique biological functions. Understanding the complexities of protein higher-order structures and dynamics requires integrated approaches, where mass spectrometry (MS) is now positioned to play a key role. One of those approaches is protein footprinting. Although the initial demonstration of footprinting was for the HOS determination of protein/nucleic acid binding, the concept was later adapted to MS-based protein HOS analysis, through which different covalent labeling approaches "mark" the solvent accessible surface area (SASA) of proteins to reflect protein HOS. Hydrogen-deuterium exchange (HDX), where deuterium in D2O replaces hydrogen of the backbone amides, is the most common example of footprinting. Its advantage is that the footprint reflects SASA and hydrogen bonding, whereas one drawback is the labeling is reversible. Another example of footprinting is slow irreversible labeling of functional groups on amino acid side chains by targeted reagents with high specificity, probing structural changes at selected sites. A third footprinting approach is by reactions with fast, irreversible labeling species that are highly reactive and footprint broadly several amino acid residue side chains on the time scale of submilliseconds. All of these covalent labeling approaches combine to constitute a problem-solving toolbox that enables mass spectrometry as a valuable tool for HOS elucidation. As there has been a growing need for MS-based protein footprinting in both academia and industry owing to its high throughput capability, prompt availability, and high spatial resolution, we present a summary of the history, descriptions, principles, mechanisms, and applications of these covalent labeling approaches. Moreover, their applications are highlighted according to the biological questions they can answer. This review is intended as a tutorial for MS-based protein HOS elucidation and as a reference for investigators seeking a MS-based tool to address structural questions in protein science.
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Affiliation(s)
| | | | - Michael L. Gross
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO, USA, 63130
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2
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Ducharme J, Auclair K. Use of bioconjugation with cytochrome P450 enzymes. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2017. [PMID: 28625736 DOI: 10.1016/j.bbapap.2017.06.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Bioconjugation, defined as chemical modification of biomolecules, is widely employed in biological and biophysical studies. It can expand functional diversity and enable applications ranging from biocatalysis, biosensing and even therapy. This review summarizes how chemical modifications of cytochrome P450 enzymes (P450s or CYPs) have contributed to improving our understanding of these enzymes. Genetic modifications of P450s have also proven very useful but are not covered in this review. Bioconjugation has served to gain structural information and investigate the mechanism of P450s via photoaffinity labeling, mechanism-based inhibition (MBI) and fluorescence studies. P450 surface acetylation and protein cross-linking have contributed to the investigation of protein complexes formation involving P450 and its redox partner or other P450 enzymes. Finally, covalent immobilization on polymer surfaces or electrodes has benefited the areas of biocatalysis and biosensor design. This article is part of a Special Issue entitled: Cytochrome P450 biodiversity and biotechnology, edited by Erika Plettner, Gianfranco Gilardi, Luet Wong, Vlada Urlacher, Jared Goldstone.
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Affiliation(s)
- Julie Ducharme
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec H3A 0B8, Canada
| | - Karine Auclair
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec H3A 0B8, Canada.
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3
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Going CC, Xia Z, Williams ER. Real-time HD Exchange Kinetics of Proteins from Buffered Aqueous Solution with Electrothermal Supercharging and Top-Down Tandem Mass Spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2016; 27:1019-1027. [PMID: 26919868 PMCID: PMC4865425 DOI: 10.1007/s13361-016-1350-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Revised: 01/21/2016] [Accepted: 01/22/2016] [Indexed: 06/05/2023]
Abstract
Electrothermal supercharging (ETS) with electrospray ionization produces highly charged protein ions from buffered aqueous solutions in which proteins have native folded structures. ETS increases the charge of ribonuclease A by 34%, whereas only a 6% increase in charge occurs for a reduced-alkylated form of this protein, which is unfolded and its structure is ~66% random coil in this solution. These results indicate that protein denaturation that occurs in the ESI droplets is the primary mechanism for ETS. ETS does not affect the extent of solution-phase hydrogen-deuterium exchange (HDX) that occurs for four proteins that have significantly different structures in solution, consistent with a droplet lifetime that is considerably shorter than observable rates of HDX. Rate constants for HDX of ubiquitin are obtained with a spatial resolution of ~1.3 residues with ETS and electron transfer dissociation of the 10+ charge-state using a single capillary containing a few μL of protein solution in which HDX continuously occurs. HDX protection at individual residues with ETS HDX is similar to that with reagent supercharging HDX and with solution-phase NMR, indicating that the high spray potentials required to induce ETS do not lead to HD scrambling. Graphical Abstract ᅟ.
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Affiliation(s)
- Catherine C Going
- Department of Chemistry, University of California, Berkeley, CA, 94720-1460, USA
| | - Zijie Xia
- Department of Chemistry, University of California, Berkeley, CA, 94720-1460, USA
| | - Evan R Williams
- Department of Chemistry, University of California, Berkeley, CA, 94720-1460, USA.
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Probing the transmembrane structure and topology of microsomal cytochrome-p450 by solid-state NMR on temperature-resistant bicelles. Sci Rep 2014; 3:2556. [PMID: 23989972 PMCID: PMC3757361 DOI: 10.1038/srep02556] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2013] [Accepted: 08/15/2013] [Indexed: 01/03/2023] Open
Abstract
Though the importance of high-resolution structure and dynamics of membrane proteins has been well recognized, optimizing sample conditions to retain the native-like folding and function of membrane proteins for Nuclear Magnetic Resonance (NMR) or X-ray measurements has been a major challenge. While bicelles have been shown to stabilize the function of membrane proteins and are increasingly utilized as model membranes, the loss of their magnetic-alignment at low temperatures makes them unsuitable to study heat-sensitive membrane proteins like cytochrome-P450 and protein-protein complexes. In this study, we report temperature resistant bicelles that can magnetically-align for a broad range of temperatures and demonstrate their advantages in the structural studies of full-length microsomal cytochrome-P450 and cytochrome-b5 by solid-state NMR spectroscopy. Our results reveal that the N-terminal region of rabbit cytochromeP4502B4, that is usually cleaved off to obtain crystal structures, is helical and has a transmembrane orientation with ~17° tilt from the lipid bilayer normal.
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Cammarata M, Lin KY, Pruet J, Liu HW, Brodbelt J. Probing the Unfolding of Myoglobin and Domain C of PARP-1 with Covalent Labeling and Top-Down Ultraviolet Photodissociation Mass Spectrometry. Anal Chem 2014; 86:2534-42. [DOI: 10.1021/ac4036235] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Michael Cammarata
- Department of Chemistry, University of Texas at Austin, 1 University
Station A5300, Austin, Texas 78212, United States
| | - Ke-Yi Lin
- Department of Chemistry, University of Texas at Austin, 1 University
Station A5300, Austin, Texas 78212, United States
| | - Jeff Pruet
- Department of Chemistry, University of Texas at Austin, 1 University
Station A5300, Austin, Texas 78212, United States
| | - Hung-wen Liu
- Department of Chemistry, University of Texas at Austin, 1 University
Station A5300, Austin, Texas 78212, United States
| | - Jennifer Brodbelt
- Department of Chemistry, University of Texas at Austin, 1 University
Station A5300, Austin, Texas 78212, United States
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6
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Architecture of a single membrane spanning cytochrome P450 suggests constraints that orient the catalytic domain relative to a bilayer. Proc Natl Acad Sci U S A 2014; 111:3865-70. [PMID: 24613931 DOI: 10.1073/pnas.1324245111] [Citation(s) in RCA: 202] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Bitopic integral membrane proteins with a single transmembrane helix play diverse roles in catalysis, cell signaling, and morphogenesis. Complete monospanning protein structures are needed to show how interaction between the transmembrane helix and catalytic domain might influence association with the membrane and function. We report crystal structures of full-length Saccharomyces cerevisiae lanosterol 14α-demethylase, a membrane monospanning cytochrome P450 of the CYP51 family that catalyzes the first postcyclization step in ergosterol biosynthesis and is inhibited by triazole drugs. The structures reveal a well-ordered N-terminal amphipathic helix preceding a putative transmembrane helix that would constrain the catalytic domain orientation to lie partly in the lipid bilayer. The structures locate the substrate lanosterol, identify putative substrate and product channels, and reveal constrained interactions with triazole antifungal drugs that are important for drug design and understanding drug resistance.
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Nehira T, Ishihara K, Matsuo K, Izumi S, Yamazaki T, Ishida A. A sensitive method based on fluorescence-detected circular dichroism for protein local structure analysis. Anal Biochem 2012; 430:179-84. [DOI: 10.1016/j.ab.2012.08.020] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2012] [Revised: 08/17/2012] [Accepted: 08/20/2012] [Indexed: 12/01/2022]
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8
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Jaffee EG, Lauber MA, Running WE, Reilly JP. In Vitro and In Vivo Chemical Labeling of Ribosomal Proteins: A Quantitative Comparison. Anal Chem 2012; 84:9355-61. [DOI: 10.1021/ac302115m] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Ethan G. Jaffee
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405-7000,
United States
| | - Matthew A. Lauber
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405-7000,
United States
| | - William E. Running
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405-7000,
United States
| | - James P. Reilly
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405-7000,
United States
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Vasicek L, O'Brien JP, Browning KS, Tao Z, Liu HW, Brodbelt JS. Mapping protein surface accessibility via an electron transfer dissociation selectively cleavable hydrazone probe. Mol Cell Proteomics 2012; 11:O111.015826. [PMID: 22393264 DOI: 10.1074/mcp.o111.015826] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A protein's surface influences its role in protein-protein interactions and protein-ligand binding. Mass spectrometry can be used to give low resolution structural information about protein surfaces and conformations when used in combination with derivatization methods that target surface accessible amino acid residues. However, pinpointing the resulting modified peptides upon enzymatic digestion of the surface-modified protein is challenging because of the complexity of the peptide mixture and low abundance of modified peptides. Here a novel hydrazone reagent (NN) is presented that allows facile identification of all modified surface residues through a preferential cleavage upon activation by electron transfer dissociation coupled with a collision activation scan to pinpoint the modified residue in the peptide sequence. Using this approach, the correlation between percent reactivity and surface accessibility is demonstrated for two biologically active proteins, wheat eIF4E and PARP-1 Domain C.
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Affiliation(s)
- Lisa Vasicek
- Department of Chemistry and Biochemistry, The University of Texas at Austin, 1 University Station A5300, Austin, TX 78712, USA
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10
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Zlocowski N, Sendra VG, Lorenz V, Villarreal MA, Jorge A, Núñez Y, Bennett EP, Clausen H, Nores GA, Irazoqui FJ. Catalytic and glycan-binding abilities of ppGalNAc-T2 are regulated by acetylation. Biochem Biophys Res Commun 2011; 410:140-5. [PMID: 21651894 DOI: 10.1016/j.bbrc.2011.05.125] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2011] [Accepted: 05/21/2011] [Indexed: 01/12/2023]
Abstract
Post-translational acetylation is an important molecular regulatory mechanism affecting the biological activity of proteins. Polypeptide GalNAc transferases (ppGalNAc-Ts) are a family of enzymes that catalyze initiation of mucin-type O-glycosylation. All ppGalNAc-Ts in mammals are type II transmembrane proteins having a Golgi lumenal region that contains a catalytic domain with glycosyltransferase activity, and a C-terminal R-type ("ricin-like") lectin domain. We investigated the effect of acetylation on catalytic activity of glycosyltransferase, and on fine carbohydrate-binding specificity of the R-type lectin domain of ppGalNAc-T2. Acetylation effect on ppGalNAc-T2 biological activity in vitro was studied using a purified human recombinant ppGalNAc-T2. Mass spectrometric analysis of acetylated ppGalNAc-T2 revealed seven acetylated amino acids (K103, S109, K111, K363, S373, K521, and S529); the first five are located in the catalytic domain. Specific glycosyltransferase activity of ppGalNAc-T2 was reduced 95% by acetylation. The last two amino acids, K521 and S529, are located in the lectin domain, and their acetylation results in alteration of the carbohydrate-binding ability of ppGalNAc-T2. Direct binding assays showed that acetylation of ppGalNAc-T2 enhances the recognition to αGalNAc residue of MUC1αGalNAc, while competitive assays showed that acetylation modifies the fine GalNAc-binding form of the lectin domain. Taken together, these findings clearly indicate that biological activity (catalytic capacity and glycan-binding ability) of ppGalNAc-T2 is regulated by acetylation.
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Affiliation(s)
- Natacha Zlocowski
- Centro de Investigaciones en Química Biológica de Córdoba, UNC-CONICET, Departamento de Química Biológica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Argentina
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11
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Saikusa K, Kono Y, Izumi S. Topology and dynamics of melittin within the liposome revealed by a combination of mass spectrometry and chemical modification. Biochem Biophys Res Commun 2010; 397:1-4. [PMID: 20398628 DOI: 10.1016/j.bbrc.2010.04.020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2010] [Accepted: 04/06/2010] [Indexed: 05/29/2023]
Abstract
The topology and dynamics of melittin within the liposome were investigated by a mass spectrometry coupled with acetylation. The MALDI-TOF MS and MALDI-QIT-TOF MS/MS analyses revealed that only N-terminal amine of melittin was dominantly acetylated in the presence of liposome although all of four primary amines were completely and rapidly acetylated in aqueous solution. This result indicates that melittin adopts the N-terminal-outside transmembrane topology within the liposome. The time course of acetylation followed the first-order kinetics at any examined temperatures (6-30 degrees C). The rate constant was less than that of the acetylation of melittin in aqueous solution. The activation energy for acetylation (74 kJ mol(-1)) was comparable to that for dissociation of a lipid monomer from the membrane, suggesting a float-like longitudinal motion of melittin within the liposome. These results demonstrate that a mass spectrometry combined with chemical modification is very efficient way for clarifying the topology and dynamics of peptides bound to the membrane.
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Affiliation(s)
- Kazumi Saikusa
- Department of Mathematical and Life Sciences, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Japan
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12
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Mendoza VL, Vachet RW. Probing protein structure by amino acid-specific covalent labeling and mass spectrometry. MASS SPECTROMETRY REVIEWS 2009; 28:785-815. [PMID: 19016300 PMCID: PMC2768138 DOI: 10.1002/mas.20203] [Citation(s) in RCA: 270] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
For many years, amino acid-specific covalent labeling has been a valuable tool to study protein structure and protein interactions, especially for systems that are difficult to study by other means. These covalent labeling methods typically map protein structure and interactions by measuring the differential reactivity of amino acid side chains. The reactivity of amino acids in proteins generally depends on the accessibility of the side chain to the reagent, the inherent reactivity of the label and the reactivity of the amino acid side chain. Peptide mass mapping with ESI- or MALDI-MS and peptide sequencing with tandem MS are typically employed to identify modification sites to provide site-specific structural information. In this review, we describe the reagents that are most commonly used in these residue-specific modification reactions, details about the proper use of these covalent labeling reagents, and information about the specific biochemical problems that have been addressed with covalent labeling strategies.
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Affiliation(s)
- Vanessa Leah Mendoza
- Department of Chemistry, University of Massachusetts Amherst, Amherst, MA 01003, USA.
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13
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Strushkevich N, Usanov SA, Plotnikov AN, Jones G, Park HW. Structural analysis of CYP2R1 in complex with vitamin D3. J Mol Biol 2008; 380:95-106. [PMID: 18511070 DOI: 10.1016/j.jmb.2008.03.065] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2008] [Revised: 03/26/2008] [Accepted: 03/27/2008] [Indexed: 01/08/2023]
Abstract
The activation of vitamin D to its hormonal form is mediated by cytochrome P450 enzymes. CYP2R1 catalyzes the initial step converting vitamin D into 25-hydroxyvitamin D. A CYP2R1 gene mutation causes an inherited form of rickets due to 25-hydroxylase deficiency. To understand the narrow substrate specificity of CYP2R1 we obtained the hemeprotein in a highly purified state, confirmed the enzyme as a vitamin D 25-hydroxylase, and solved the crystal structure of CYP2R1 in complex with vitamin D3. The CYP2R1 structure adopts a closed conformation with the substrate access channel being covered by the ordered B'-helix and slightly opened to the surface, which defines the substrate entrance point. The active site is lined by conserved, mostly hydrophobic residues. Vitamin D3 is bound in an elongated conformation with the aliphatic side-chain pointing toward the heme. The structure reveals the secosteroid binding mode in an extended active site and allows rationalization of the molecular basis of the inherited rickets associated with CYP2R1.
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14
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Mapping of cytochrome P450 2B4 substrate binding sites by photolabile probe 3-azidiamantane: Identification of putative substrate access regions. Arch Biochem Biophys 2007; 468:82-91. [DOI: 10.1016/j.abb.2007.09.017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2007] [Revised: 09/12/2007] [Accepted: 09/22/2007] [Indexed: 11/20/2022]
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15
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Iyanagi T. Molecular mechanism of phase I and phase II drug-metabolizing enzymes: implications for detoxification. ACTA ACUST UNITED AC 2007; 260:35-112. [PMID: 17482904 DOI: 10.1016/s0074-7696(06)60002-8] [Citation(s) in RCA: 154] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Enzymes that catalyze the biotransformation of drugs and xenobiotics are generally referred to as drug-metabolizing enzymes (DMEs). DMEs can be classified into two main groups: oxidative or conjugative. The NADPH-cytochrome P450 reductase (P450R)/cytochrome P450 (P450) electron transfer systems are oxidative enzymes that mediate phase I reactions, whereas the UDP-glucuronosyltransferases (UGTs) are conjugative enzymes that mediate phase II enzymes. Both enzyme systems are localized to the endoplasmic reticulum (ER) where a number of drugs are sequentially metabolized. DMEs, including P450s and UGTs, generally have a highly plastic active site that can accommodate a wide variety of substrates. The P450 and UGT genes constitute a supergene family, in which UGT proteins are encoded by distinct genes and a complex gene. Both the P450 and UGT genes have evolved to diversify their functions. This chapter reviews advances in understanding the structure and function of the P450R/P450 and UGT enzyme systems. In particular, the coordinate biotransformation of xenobiotics by phase I and II enzymes in the ER membrane is examined.
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Affiliation(s)
- Takashi Iyanagi
- Biometal Science Laboratory, RIKEN SPring-8 Center, Harima Institute, Hyogo 679-5148, Japan
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16
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Mukai H, Tsurugizawa T, Murakami G, Kominami S, Ishii H, Ogiue-Ikeda M, Takata N, Tanabe N, Furukawa A, Hojo Y, Ooishi Y, Morrison JH, Janssen WGM, Rose JA, Chambon P, Kato S, Izumi S, Yamazaki T, Kimoto T, Kawato S. Rapid modulation of long-term depression and spinogenesis via synaptic estrogen receptors in hippocampal principal neurons. J Neurochem 2007; 100:950-67. [PMID: 17266735 DOI: 10.1111/j.1471-4159.2006.04264.x] [Citation(s) in RCA: 162] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Rapid modulation of hippocampal synaptic plasticity by estrogen has long been a hot topic, but analysis of molecular mechanisms via synaptic estrogen receptors has been seriously difficult. Here, two types of independent synaptic plasticity, long-term depression (LTD) and spinogenesis, were investigated, in response to 17beta-estradiol and agonists of estrogen receptors using hippocampal slices from adult male rats. Multi-electrode investigations demonstrated that estradiol rapidly enhanced LTD not only in CA1 but also in CA3 and dentate gyrus. Dendritic spine morphology analysis demonstrated that the density of thin type spines was selectively increased in CA1 pyramidal neurons within 2 h after application of 1 nm estradiol. This enhancement of spinogenesis was completely suppressed by mitogen-activated protein (MAP) kinase inhibitor. Only the estrogen receptor (ER) alpha agonist, (propyl-pyrazole-trinyl)tris-phenol (PPT), induced the same enhancing effect as estradiol on both LTD and spinogenesis in the CA1. The ERbeta agonist, (4-hydroxyphenyl)-propionitrile (DPN), suppressed LTD and did not affect spinogenesis. Because the mode of synaptic modulations by estradiol was mostly the same as that by the ERalpha agonist, a search was made for synaptic ERalpha using purified RC-19 antibody qualified using ERalpha knockout (KO) mice. Localization of ERalpha in spines of principal glutamatergic neurons was demonstrated using immunogold electron microscopy and immunohistochemistry. ERalpha was also located in nuclei, cytoplasm and presynapses.
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Affiliation(s)
- Hideo Mukai
- Department of Biophysics and Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Komaba, Meguro, Tokyo, Japan
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17
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Abstract
The ClC family of chloride channels and transporters includes several members in which mutations have been associated with human disease. An understanding of the structure-function relationships of these proteins is essential for defining the molecular mechanisms underlying pathogenesis. To date, the X-ray crystal structures of prokaryotic ClC transporter proteins have been used to model the membrane domains of eukaryotic ClC channel-forming proteins. Clearly, the fidelity of these models must be evaluated empirically. In the present study, biochemical tools were used to define the membrane domain boundaries of the eukaryotic protein, ClC-2, a chloride channel mutated in cases of idiopathic epilepsy. The membrane domain boundaries of purified ClC-2 and accessible cysteine residues were determined after its functional reconstitution into proteoliposomes, labelling using a thiol reagent and proteolytic digestion. Subsequently, the lipid-embedded and soluble fragments generated by trypsin-mediated proteolysis were studied by MS and coverage of approx. 71% of the full-length protein was determined. Analysis of these results revealed that the membrane-delimited boundaries of the N- and C-termini of ClC-2 and the position of several extramembrane loops determined by these methods are largely similar to those predicted on the basis of the prokaryotic protein [ecClC (Escherichia coli ClC)] structures. These studies provide direct biochemical evidence supporting the relevance of the prokaryotic ClC protein structures towards understanding the structure of mammalian ClC channel-forming proteins.
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Affiliation(s)
- Mohabir Ramjeesingh
- Programme of Structural Biology and Biochemistry, Research Institute of the Hospital for Sick Children, 555 University Avenue, Toronto, ON, Canada M5G 1X8
| | - Canhui Li
- Programme of Structural Biology and Biochemistry, Research Institute of the Hospital for Sick Children, 555 University Avenue, Toronto, ON, Canada M5G 1X8
| | - Yi-Min She
- Programme of Structural Biology and Biochemistry, Research Institute of the Hospital for Sick Children, 555 University Avenue, Toronto, ON, Canada M5G 1X8
| | - Christine E. Bear
- Programme of Structural Biology and Biochemistry, Research Institute of the Hospital for Sick Children, 555 University Avenue, Toronto, ON, Canada M5G 1X8
- To whom correspondence should be addressed (email )
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18
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Nikfarjam L, Izumi S, Yamazaki T, Kominami S. The interaction of cytochrome P450 17α with NADPH-cytochrome P450 reductase, investigated using chemical modification and MALDI-TOF mass spectrometry. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2006; 1764:1126-31. [PMID: 16713412 DOI: 10.1016/j.bbapap.2006.04.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2006] [Revised: 03/22/2006] [Accepted: 04/01/2006] [Indexed: 11/28/2022]
Abstract
The lysine residues of guinea pig P450 17alpha were acetylated by acetic anhydride in the absence and presence of NADPH cytochrome P450 reductase (CPR). Eight acetylated peptides were identified in the MALDI-TOF mass spectra of the tryptic fragments from the P450 acetylated without CPR in the limited reaction time of 15 min at ice temperature. The presence of CPR during the acetylation of P450 17alpha prevented double acetylations at K326 and K327 in the J-helix. The activity of P450 17alpha was decreased to 35% by the acetylation, but almost no inactivation was detected in the P450 after acetylation in the presence of CPR. This protection from inactivation shows the importance of K326 and/or K327 in the J-helix of P450 17alpha in the interaction between the two enzymes. Our results provided the first experimental evidence for the importance of the J-helix of P450 in the interaction with CPR. The interaction of P450 17alpha with CPR on the membrane is discussed based on the results of this study, which used molecular modeling.
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Affiliation(s)
- Laleh Nikfarjam
- Graduate School of Biosphere Science, Hiroshima University, 1-4-4 Kagamiyama, Higashihiroshima 739-8528, Japan
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Johnson EF, Stout CD. Structural diversity of human xenobiotic-metabolizing cytochrome P450 monooxygenases. Biochem Biophys Res Commun 2005; 338:331-6. [PMID: 16157296 DOI: 10.1016/j.bbrc.2005.08.190] [Citation(s) in RCA: 109] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2005] [Accepted: 08/25/2005] [Indexed: 12/24/2022]
Abstract
Cytochrome P450 monooxygenases provide important pathways for the metabolic clearance of drugs and toxins in humans. These enzymes are expressed from multiple genes and exhibit complex patterns of differential and overlapping substrate selectivity. Recent structures of microsomal P450s determined by X-ray crystallography have provided a structural basis for understanding differences in substrate recognition. This review will describe similarities and differences in the active site structures of four human microsomal cytochrome P450 monooxygenases, 2A6, 2C8, 2C9, and 3A4, that contribute extensively to drug and toxin metabolism.
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Affiliation(s)
- Eric F Johnson
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA.
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Nesatyy VJ, Rutishauser BV, Eggen RIL, Suter MJF. Identification of the estrogen receptor Cd-binding sites by chemical modification. Analyst 2005; 130:1087-97. [PMID: 15965534 DOI: 10.1039/b501192b] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The widely reported interactions of the estrogen receptor (ER) with endocrine disrupting chemicals (EDCs) present in the environment gave raise to public concern and led to a number of screening and testing initiatives on the international level. Recent studies indicated that certain heavy metals, including cadmium, can mimic the effects of the endogenous estrogen receptor agonist 17beta-estradiol, and lead to estrogen receptor activation. Previous studies of the chimeric proteins, which incorporate the ligand-binding domain of the human ER, identified Cys 381, Cys 447, Glu 523, His 524 and Asp 538 as possible sites of interactions with cadmium. In the present study we utilized the rainbow trout ER ligand-binding domain fused to glutathione-S-transferase, and used Cd-shielding against various types of chemical modification of the fusion protein to study non-covalent interactions between the ER and Cd. The distribution of exposed and shielded residues allowed to identify amino acid residues involved in the interaction. Our data indicated preferential protection of Cys groups by cadmium, suggesting their involvement in the interaction. This supports data found in the literature on the strong binding affinity of the thiol group towards metals. However, not all Cys in the fusion protein sequence were protected against chemical modification, illustrating the importance of their chemical environment. In general, the location of rtER-LBD Cys residues implicated in Cd interactions did not confirm assignments made by alanine-scanning mutagenesis for the hER, probably due to differences in experimental setup and fusion proteins used. The involvement of other functional groups such as carboxylic acids in the Cd interactions, though not confirmed, can not be completely ruled out due to the general limitations of the chemical modification approach discussed in detail. Suggestions for an improved experimental setup were made.
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Affiliation(s)
- Victor J Nesatyy
- Department of Environmental Toxicology, Swiss Federal Institute for Environmental Science and Technology, 8600 Dubendorf, Switzerland
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