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The Structure of the Bifunctional Everninomicin Biosynthetic Enzyme EvdMO1 Suggests Independent Activity of the Fused Methyltransferase-Oxidase Domains.
Starbird CA, Perry NA, Chen Q, Berndt S, Yamakawa I, Loukachevitch LV, Limbrick EM, Bachmann BO, Iverson TM, McCulloch KM
(2018) Biochemistry 57: 6827-6837
MeSH Terms: Amino Acid Sequence, Aminoglycosides, Bacterial Proteins, Biosynthetic Pathways, Catalytic Domain, Conserved Sequence, Crystallography, X-Ray, Gene Fusion, Genes, Bacterial, Methyltransferases, Micromonospora, Models, Molecular, Oxygenases, Protein Interaction Domains and Motifs, Sequence Homology, Amino Acid
Show Abstract · Added April 1, 2019
Members of the orthosomycin family of natural products are decorated polysaccharides with potent antibiotic activity and complex biosynthetic pathways. The defining feature of the orthosomycins is an orthoester linkage between carbohydrate moieties that is necessary for antibiotic activity and is likely formed by a family of conserved oxygenases. Everninomicins are octasaccharide orthosomycins produced by Micromonospora carbonacea that have two orthoester linkages and a methylenedioxy bridge, three features whose formation logically requires oxidative chemistry. Correspondingly, the evd gene cluster encoding everninomicin D encodes two monofunctional nonheme iron, α-ketoglutarate-dependent oxygenases and one bifunctional enzyme with an N-terminal methyltransferase domain and a C-terminal oxygenase domain. To investigate whether the activities of these domains are linked in the bifunctional enzyme EvdMO1, we determined the structure of the N-terminal methyltransferase domain to 1.1 Å and that of the full-length protein to 3.35 Å resolution. Both domains of EvdMO1 adopt the canonical folds of their respective superfamilies and are connected by a short linker. Each domain's active site is oriented such that it faces away from the other domain, and there is no evidence of a channel connecting the two. Our results support EvdMO1 working as a bifunctional enzyme with independent catalytic activities.
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15 MeSH Terms
Dual cyclooxygenase-fatty acid amide hydrolase inhibitor exploits novel binding interactions in the cyclooxygenase active site.
Goodman MC, Xu S, Rouzer CA, Banerjee S, Ghebreselasie K, Migliore M, Piomelli D, Marnett LJ
(2018) J Biol Chem 293: 3028-3038
MeSH Terms: Amidohydrolases, Catalytic Domain, Cyclooxygenase Inhibitors, Isoenzymes, Phenylcarbamates, Phenylpropionates, Prostaglandin-Endoperoxide Synthases, Protein Binding, Stereoisomerism, Substrate Specificity
Show Abstract · Added April 22, 2018
The cyclooxygenases COX-1 and COX-2 oxygenate arachidonic acid (AA) to prostaglandin H (PGH). COX-2 also oxygenates the endocannabinoids 2-arachidonoylglycerol (2-AG) and arachidonoylethanolamide (AEA) to the corresponding PGH analogs. Both enzymes are targets of nonsteroidal anti-inflammatory drugs (NSAIDs), but NSAID-mediated COX inhibition is associated with gastrointestinal toxicity. One potential strategy to counter this toxicity is to also inhibit fatty acid amide hydrolase (FAAH), which hydrolyzes bioactive fatty acid ethanolamides (FAEs) into fatty acids and ethanolamine. Here, we investigated the mechanism of COX inhibition by ARN2508, an NSAID that inhibits both COXs and FAAH with high potency, target selectivity, and decreased gastrointestinal toxicity in mouse models, presumably due to its ability to increase levels of FAEs. A 2.27-Å-resolution X-ray crystal structure of the COX-2·()-ARN2508 complex reveals that ARN2508 adopts a binding pose similar to that of its parent NSAID flurbiprofen. However, ARN2508's alkyl tail is inserted deep into the top channel, an active site region not exploited by any previously reported NSAID. As for flurbiprofen, ARN2508's potency is highly dependent on the configuration of the α-methyl group. Thus, ()-ARN2508 is more potent than ()-ARN2508 for inhibition of AA oxygenation by both COXs and 2-AG oxygenation by COX-2. Also, similarly to ()-flurbiprofen, ()-ARN2508 exhibits substrate selectivity for inhibition of 2-AG oxygenation. Site-directed mutagenesis confirms the importance of insertion of the alkyl tail into the top channel for ()-ARN2508's potency and suggests a role for Ser-530 as a determinant of the inhibitor's slow rate of inhibition compared with that of ()-flurbiprofen.
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10 MeSH Terms
Selective base excision repair of DNA damage by the non-base-flipping DNA glycosylase AlkC.
Shi R, Mullins EA, Shen XX, Lay KT, Yuen PK, David SS, Rokas A, Eichman BF
(2018) EMBO J 37: 63-74
MeSH Terms: Adenine, Alkylation, Amino Acid Sequence, Bacillus cereus, Catalytic Domain, Crystallography, X-Ray, DNA Adducts, DNA Damage, DNA Glycosylases, DNA Repair, Models, Molecular, Protein Conformation, Sequence Homology
Show Abstract · Added March 21, 2018
DNA glycosylases preserve genome integrity and define the specificity of the base excision repair pathway for discreet, detrimental modifications, and thus, the mechanisms by which glycosylases locate DNA damage are of particular interest. Bacterial AlkC and AlkD are specific for cationic alkylated nucleobases and have a distinctive HEAT-like repeat (HLR) fold. AlkD uses a unique non-base-flipping mechanism that enables excision of bulky lesions more commonly associated with nucleotide excision repair. In contrast, AlkC has a much narrower specificity for small lesions, principally N3-methyladenine (3mA). Here, we describe how AlkC selects for and excises 3mA using a non-base-flipping strategy distinct from that of AlkD. A crystal structure resembling a catalytic intermediate complex shows how AlkC uses unique HLR and immunoglobulin-like domains to induce a sharp kink in the DNA, exposing the damaged nucleobase to active site residues that project into the DNA This active site can accommodate and excise N3-methylcytosine (3mC) and N1-methyladenine (1mA), which are also repaired by AlkB-catalyzed oxidative demethylation, providing a potential alternative mechanism for repair of these lesions in bacteria.
© 2017 The Authors.
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13 MeSH Terms
A Polymerase With Potential: The Fe-S Cluster in Human DNA Primase.
Holt ME, Salay LE, Chazin WJ
(2017) Methods Enzymol 595: 361-390
MeSH Terms: Catalytic Domain, DNA, DNA Primase, DNA Primers, DNA Replication, Humans, Iron-Sulfur Proteins, Oxidation-Reduction, RNA, Sequence Analysis
Show Abstract · Added March 24, 2018
Replication of DNA in eukaryotes is primarily executed by the combined action of processive DNA polymerases δ and ɛ. These enzymes cannot initiate synthesis of new DNA without the presence of a primer on the template ssDNA. The primers on both the leading and lagging strands are generated by DNA polymerase α-primase (pol-prim). DNA primase is a DNA-dependent RNA polymerase that synthesizes the first ~10 nucleotides and then transfers the substrate to polymerase α to complete primer synthesis. The mechanisms governing the coordination and handoff between primase and polymerase α are largely unknown. Isolated DNA primase contains a [4Fe-4S] cluster that has been shown to serve as a redox switch modulating DNA binding affinity. This discovery suggests a mechanism for modulating the priming activity of primase and handoff to polymerase α. In this chapter, we briefly discuss the current state of knowledge of primase structure and function, including the role of its iron-sulfur cluster. This is followed by providing the methods for expressing, purifying, and biophysically/structurally characterizing primase and its iron-sulfur cluster-containing domain, p58C.
© 2017 Elsevier Inc. All rights reserved.
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10 MeSH Terms
Horse Liver Alcohol Dehydrogenase: Zinc Coordination and Catalysis.
Plapp BV, Savarimuthu BR, Ferraro DJ, Rubach JK, Brown EN, Ramaswamy S
(2017) Biochemistry 56: 3632-3646
MeSH Terms: 2,2'-Dipyridyl, Adenosine Diphosphate Ribose, Alcohol Dehydrogenase, Animals, Catalytic Domain, Crystallography, X-Ray, Formamides, Horses, Kinetics, Liver, Models, Molecular, NAD, Phenanthrolines, Protein Binding, Protein Conformation, Water, Zinc
Show Abstract · Added August 31, 2017
During catalysis by liver alcohol dehydrogenase (ADH), a water bound to the catalytic zinc is replaced by the oxygen of the substrates. The mechanism might involve a pentacoordinated zinc or a double-displacement reaction with participation by a nearby glutamate residue, as suggested by studies of human ADH3, yeast ADH1, and some other tetrameric ADHs. Zinc coordination and participation of water in the enzyme mechanism were investigated by X-ray crystallography. The apoenzyme and its complex with adenosine 5'-diphosphoribose have an open protein conformation with the catalytic zinc in one position, tetracoordinated by Cys-46, His-67, Cys-174, and a water molecule. The bidentate chelators 2,2'-bipyridine and 1,10-phenanthroline displace the water and form a pentacoordinated zinc. The enzyme-NADH complex has a closed conformation similar to that of ternary complexes with coenzyme and substrate analogues; the coordination of the catalytic zinc is similar to that found in the apoenzyme, except that a minor, alternative position for the catalytic zinc is ∼1.3 Å from the major position and closer to Glu-68, which could form the alternative coordination to the catalytic zinc. Complexes with NADH and N-1-methylhexylformamide or N-benzylformamide (or with NAD and fluoro alcohols) have the classical tetracoordinated zinc, and no water is bound to the zinc or the nicotinamide rings. The major forms of the enzyme in the mechanism have a tetracoordinated zinc, where the carboxylate group of Glu-68 could participate in the exchange of water and substrates on the zinc. Hydride transfer in the Michaelis complexes does not involve a nearby water.
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17 MeSH Terms
Roles of Human CYP2A6 and Monkey CYP2A24 and 2A26 Cytochrome P450 Enzymes in the Oxidation of 2,5,2',5'-Tetrachlorobiphenyl.
Shimada T, Kakimoto K, Takenaka S, Koga N, Uehara S, Murayama N, Yamazaki H, Kim D, Guengerich FP, Komori M
(2016) Drug Metab Dispos 44: 1899-1909
MeSH Terms: Animals, Catalysis, Catalytic Domain, Cytochrome P-450 CYP2A6, Cytochrome P-450 Enzyme System, Haplorhini, Humans, Ligands, Molecular Docking Simulation, Oxidation-Reduction, Polychlorinated Biphenyls, Protein Binding
Show Abstract · Added March 14, 2018
2,5,2',5'-Tetrachlorobiphenyl (TCB) induced type I binding spectra with cytochrome P450 (P450) 2A6 and 2A13, with K values of 9.4 and 0.51 µM, respectively. However, CYP2A6 oxidized 2,5,2',5'-TCB to form 4-hydroxylated products at a much higher rate (∼1.0 minute) than CYP2A13 (∼0.02 minute) based on analysis by liquid chromatography-tandem mass spectrometry. Formation of 4-hydroxy-2,5,2',5'-TCB by CYP2A6 was greater than that of 3-hydroxy-2,5,2',5'-TCB and three other hydroxylated products. Several human P450 enzymes, including CYP1A1, 1A2, 1B1, 2B6, 2D6, 2E1, 2C9, and 3A4, did not show any detectable activities in oxidizing 2,5,2',5'-TCB. Cynomolgus monkey CYP2A24, which shows 95% amino acid identity to human CYP2A6, catalyzed 4-hydroxylation of 2,5,2',5'-TCB at a higher rate (∼0.3 minute) than CYP2A26 (93% identity to CYP2A6, ∼0.13 minute) and CYP2A23 (94% identity to CYP2A13, ∼0.008 minute). None of these human and monkey CYP2A enzymes were catalytically active in oxidizing other TCB congeners, such as 2,4,3',4'-, 3,4,3',4'-, and 3,5,3',5'-TCB. Molecular docking analysis suggested that there are different orientations of interaction of 2,5,2',5'-TCB with the active sites (over the heme) of human and monkey CYP2A enzymes, and that ligand interaction energies (U values) of bound protein-ligand complexes show structural relationships of interaction of TCBs and other ligands with active sites of CYP2A enzymes. Catalytic differences in human and monkey CYP2A enzymes in the oxidation of 2,5,2',5'-TCB are suggested to be due to amino acid changes at substrate recognition sites, i.e., V110L, I209S, I300F, V365M, S369G, and R372H, based on the comparison of primary sequences.
Copyright © 2016 by The American Society for Pharmacology and Experimental Therapeutics.
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12 MeSH Terms
Human sterol 14α-demethylase as a target for anticancer chemotherapy: towards structure-aided drug design.
Hargrove TY, Friggeri L, Wawrzak Z, Sivakumaran S, Yazlovitskaya EM, Hiebert SW, Guengerich FP, Waterman MR, Lepesheva GI
(2016) J Lipid Res 57: 1552-63
MeSH Terms: 14-alpha Demethylase Inhibitors, Antifungal Agents, Antineoplastic Agents, Antiprotozoal Agents, Catalytic Domain, Cell Line, Tumor, Cholestadienols, Crystallography, X-Ray, Drug Design, Drug Screening Assays, Antitumor, Humans, Hydrogen Bonding, Lanosterol, Models, Molecular, Protein Binding, Protein Conformation, alpha-Helical, Sterol 14-Demethylase
Show Abstract · Added April 6, 2017
Rapidly multiplying cancer cells synthesize greater amounts of cholesterol to build their membranes. Cholesterol-lowering drugs (statins) are currently in clinical trials for anticancer chemotherapy. However, given at higher doses, statins cause serious side effects by inhibiting the formation of other biologically important molecules derived from mevalonate. Sterol 14α-demethylase (CYP51), which acts 10 steps downstream, is potentially a more specific drug target because this portion of the pathway is fully committed to cholesterol production. However, screening a variety of commercial and experimental inhibitors of microbial CYP51 orthologs revealed that most of them (including all clinical antifungals) weakly inhibit human CYP51 activity, even if they display high apparent spectral binding affinity. Only one relatively potent compound, (R)-N-(1-(3,4'-difluorobiphenyl-4-yl)-2-(1H-imidazol-1-yl)ethyl)-4-(5-phenyl-1,3,4-oxadiazol-2-yl)benzamide (VFV), was identified. VFV has been further tested in cellular experiments and found to decrease proliferation of different cancer cell types. The crystal structures of human CYP51-VFV complexes (2.0 and 2.5 Å) both display a 2:1 inhibitor/enzyme stoichiometry, provide molecular insights regarding a broader substrate profile, faster catalysis, and weaker susceptibility of human CYP51 to inhibition, and outline directions for the development of more potent inhibitors.
Copyright © 2016 by the American Society for Biochemistry and Molecular Biology, Inc.
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17 MeSH Terms
The three Type 2A protein phosphatases, PP2Ac, PP4c and PP6c, are differentially regulated by Alpha4.
LeNoue-Newton ML, Wadzinski BE, Spiller BW
(2016) Biochem Biophys Res Commun 475: 64-9
MeSH Terms: Catalytic Domain, Gene Knockdown Techniques, HEK293 Cells, HeLa Cells, Humans, Intracellular Signaling Peptides and Proteins, Phosphoprotein Phosphatases, Protein Phosphatase 2
Show Abstract · Added March 15, 2018
Alpha4 is a non-canonical regulatory subunit of Type 2A protein phosphatases that interacts directly with the phosphatase catalytic subunits (PP2Ac, PP4c, and PP6c) and is upregulated in a variety of cancers. Alpha4 modulates phosphatase expression levels and activity, but the molecular mechanism of this regulation is unclear, and the extent to which the various Type 2A catalytic subunits associate with Alpha4 is also unknown. To determine the relative fractions of the Type 2A catalytic subunits associated with Alpha4, we conducted Alpha4 immunodepletion experiments in HEK293T cells and found that a significant fraction of total PP6c is associated with Alpha4, whereas a minimal fraction of total PP2Ac is associated with Alpha4. To facilitate studies of phosphatases in the presence of mutant or null Alpha4 alleles, we developed a facile and rapid method to simultaneously knockdown and rescue Alpha4 in tissue culture cells. This approach has the advantage that levels of endogenous Alpha4 are dramatically reduced by shRNA expression thereby simplifying interpretation of mutant phenotypes. We used this system to show that knockdown of Alpha4 preferentially impacts the expression of PP4c and PP6c compared to expression levels of PP2Ac.
Copyright © 2016. Published by Elsevier Inc.
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8 MeSH Terms
Kinetic analysis of bypass of 7,8-dihydro-8-oxo-2'-deoxyguanosine by the catalytic core of yeast DNA polymerase η.
Xue Q, Zhong M, Liu B, Tang Y, Wei Z, Guengerich FP, Zhang H
(2016) Biochimie 121: 161-9
MeSH Terms: Catalytic Domain, DNA-Directed DNA Polymerase, Deoxyguanosine, Kinetics, Pyrimidine Nucleotides
Show Abstract · Added March 14, 2018
Reactive oxygen species damage DNA bases to produce 7,8-dihydro-8-oxo-2'-deoxyguanosine (8-oxoG), which results in G:C to T:A transversions. To better understand mechanisms of dNTP incorporation opposite 8-oxoG, we performed pre-steady-state kinetic analysis of nucleotide incorporation using the catalytic core of yeast DNA polymerase η (Pol ηcore, residues 1-513) instead of full-length Pol η, eliminating potential effects of the C-terminal C2H2 sequence motif on dNTP incorporation. Kinetic analysis showed that Pol ηcore preferred to incorporate dCTP opposite 8-oxoG. A lack of a pre-steady-state kinetic burst for Pol ηcore suggested that dCTP incorporation is slower than the dissociation of the polymerase from DNA. The extension products beyond the 8-oxoG were determined by LC-MS/MS and showed that 57% of the products corresponded to the correct incorporation (C) and 43% corresponded to dATP misincorporation. More dATP was incorporated opposite 8-oxoG with a mixture of dNTPs than predicted using only a single dNTP. The kinetic analysis of 8-oxoG bypass by yeast DNA Pol ηcore provides further understanding of the mechanism of mutation at this oxidation lesion with yeast DNA polymerase η.
Copyright © 2015. Published by Elsevier B.V.
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5 MeSH Terms
A Structural Study of CESA1 Catalytic Domain of Arabidopsis Cellulose Synthesis Complex: Evidence for CESA Trimers.
Vandavasi VG, Putnam DK, Zhang Q, Petridis L, Heller WT, Nixon BT, Haigler CH, Kalluri U, Coates L, Langan P, Smith JC, Meiler J, O'Neill H
(2016) Plant Physiol 170: 123-35
MeSH Terms: Arabidopsis, Arabidopsis Proteins, Catalytic Domain, Cellulose, Escherichia coli, Glucosyltransferases, Microscopy, Electron, Transmission, Models, Molecular, Multiprotein Complexes, Protein Multimerization, Protein Structure, Secondary, Recombinant Proteins, Scattering, Small Angle, X-Ray Diffraction
Show Abstract · Added February 5, 2016
A cellulose synthesis complex with a "rosette" shape is responsible for synthesis of cellulose chains and their assembly into microfibrils within the cell walls of land plants and their charophyte algal progenitors. The number of cellulose synthase proteins in this large multisubunit transmembrane protein complex and the number of cellulose chains in a microfibril have been debated for many years. This work reports a low resolution structure of the catalytic domain of CESA1 from Arabidopsis (Arabidopsis thaliana; AtCESA1CatD) determined by small-angle scattering techniques and provides the first experimental evidence for the self-assembly of CESA into a stable trimer in solution. The catalytic domain was overexpressed in Escherichia coli, and using a two-step procedure, it was possible to isolate monomeric and trimeric forms of AtCESA1CatD. The conformation of monomeric and trimeric AtCESA1CatD proteins were studied using small-angle neutron scattering and small-angle x-ray scattering. A series of AtCESA1CatD trimer computational models were compared with the small-angle x-ray scattering trimer profile to explore the possible arrangement of the monomers in the trimers. Several candidate trimers were identified with monomers oriented such that the newly synthesized cellulose chains project toward the cell membrane. In these models, the class-specific region is found at the periphery of the complex, and the plant-conserved region forms the base of the trimer. This study strongly supports the "hexamer of trimers" model for the rosette cellulose synthesis complex that synthesizes an 18-chain cellulose microfibril as its fundamental product.
© 2016 American Society of Plant Biologists. All Rights Reserved.
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14 MeSH Terms