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Gagnon SML, Legg MSG, Polakowski R, Letts JA, Persson M, Lin S, Zheng RB, Rempel B, Schuman B, Haji-Ghassemi O, Borisova SN, Palcic MM, Evans SV. Conserved residues Arg188 and Asp302 are critical for active site organization and catalysis in human ABO(H) blood group A and B glycosyltransferases. Glycobiology 2018; 28:624-636. [PMID: 29873711 PMCID: PMC6054251 DOI: 10.1093/glycob/cwy051] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2018] [Accepted: 06/05/2018] [Indexed: 01/02/2023] Open
Abstract
Homologous glycosyltransferases GTA and GTB perform the final step in human ABO(H) blood group A and B antigen synthesis by transferring the sugar moiety from donor UDP-GalNAc/UDP-Gal to the terminal H antigen disaccharide acceptor. Like other GT-A fold family 6 glycosyltransferases, GTA and GTB undergo major conformational changes in two mobile regions, the C-terminal tail and internal loop, to achieve the closed, catalytic state. These changes are known to establish a salt bridge network among conserved active site residues Arg188, Asp211 and Asp302, which move to accommodate a series of discrete donor conformations while promoting loop ordering and formation of the closed enzyme state. However, the individual significance of these residues in linking these processes remains unclear. Here, we report the kinetics and high-resolution structures of GTA/GTB mutants of residues 188 and 302. The structural data support a conserved salt bridge network critical to mobile polypeptide loop organization and stabilization of the catalytically competent donor conformation. Consistent with the X-ray crystal structures, the kinetic data suggest that disruption of this salt bridge network has a destabilizing effect on the transition state, emphasizing the importance of Arg188 and Asp302 in the glycosyltransfer reaction mechanism. The salt bridge network observed in GTA/GTB structures during substrate binding appears to be conserved not only among other Carbohydrate Active EnZyme family 6 glycosyltransferases but also within both retaining and inverting GT-A fold glycosyltransferases. Our findings augment recently published crystal structures, which have identified a correlation between donor substrate conformational changes and mobile loop ordering.
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Affiliation(s)
- Susannah M L Gagnon
- Department of Biochemistry & Microbiology, University of Victoria, STN CSC, Victoria, BC, Canada
| | - Max S G Legg
- Department of Biochemistry & Microbiology, University of Victoria, STN CSC, Victoria, BC, Canada
| | - Robert Polakowski
- Department of Chemistry, University of Alberta, Edmonton, AB, Canada
| | - James A Letts
- Department of Biochemistry & Microbiology, University of Victoria, STN CSC, Victoria, BC, Canada
| | - Mattias Persson
- Carlsberg Laboratory, Gamle Carlsberg Vej 4-10, Copenhagen V, Denmark
| | - Shuangjun Lin
- Department of Chemistry, University of Alberta, Edmonton, AB, Canada
| | | | - Brian Rempel
- Department of Chemistry, University of Alberta, Edmonton, AB, Canada
| | - Brock Schuman
- Department of Biochemistry & Microbiology, University of Victoria, STN CSC, Victoria, BC, Canada
| | - Omid Haji-Ghassemi
- Department of Biochemistry & Microbiology, University of Victoria, STN CSC, Victoria, BC, Canada
| | - Svetlana N Borisova
- Department of Biochemistry & Microbiology, University of Victoria, STN CSC, Victoria, BC, Canada
| | - Monica M Palcic
- Department of Biochemistry & Microbiology, University of Victoria, STN CSC, Victoria, BC, Canada
- Department of Chemistry, University of Alberta, Edmonton, AB, Canada
- Carlsberg Laboratory, Gamle Carlsberg Vej 4-10, Copenhagen V, Denmark
| | - Stephen V Evans
- Department of Biochemistry & Microbiology, University of Victoria, STN CSC, Victoria, BC, Canada
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Brockhausen I. Crossroads between Bacterial and Mammalian Glycosyltransferases. Front Immunol 2014; 5:492. [PMID: 25368613 PMCID: PMC4202792 DOI: 10.3389/fimmu.2014.00492] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Accepted: 09/23/2014] [Indexed: 11/26/2022] Open
Abstract
Bacterial glycosyltransferases (GT) often synthesize the same glycan linkages as mammalian GT; yet, they usually have very little sequence identity. Nevertheless, enzymatic properties, folding, substrate specificities, and catalytic mechanisms of these enzyme proteins may have significant similarity. Thus, bacterial GT can be utilized for the enzymatic synthesis of both bacterial and mammalian types of complex glycan structures. A comparison is made here between mammalian and bacterial enzymes that synthesize epitopes found in mammalian glycoproteins, and those found in the O antigens of Gram-negative bacteria. These epitopes include Thomsen–Friedenreich (TF or T) antigen, blood group O, A, and B, type 1 and 2 chains, Lewis antigens, sialylated and fucosylated structures, and polysialic acids. Many different approaches can be taken to investigate the substrate binding and catalytic mechanisms of GT, including crystal structure analyses, mutations, comparison of amino acid sequences, NMR, and mass spectrometry. Knowledge of the protein structures and functions helps to design GT for specific glycan synthesis and to develop inhibitors. The goals are to develop new strategies to reduce bacterial virulence and to synthesize vaccines and other biologically active glycan structures.
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Affiliation(s)
- Inka Brockhausen
- Department of Medicine, Queen's University , Kingston, ON , Canada ; Department of Biomedical and Molecular Sciences, Queen's University , Kingston, ON , Canada
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3
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Soya N, Fang Y, Palcic MM, Klassen JS. Trapping and characterization of covalent intermediates of mutant retaining glycosyltransferases. Glycobiology 2010; 21:547-52. [PMID: 21098513 DOI: 10.1093/glycob/cwq190] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The enzymatic mechanism by which retaining glycosyltransferases (GTs) transfer monosaccharides with net retention of the anomeric configuration has, so far, resisted elucidation. Here, direct detection of covalent glycosyl-enzyme intermediates for mutants of two model retaining GTs, the human blood group synthesizing α-(1 → 3)-N-acetylgalactosaminyltransferase (GTA) and α-(1 → 3)-galactosyltransferase (GTB) mutants, by mass spectrometry (MS) is reported. Incubation of mutants of GTA or GTB, in which the putative catalytic nucleophile Glu(303) was replaced with Cys (i.e. GTA(E303C) and GTB(E303C)), with their respective donor substrate results in a covalent intermediate. Tandem MS analysis using collision-induced dissociation confirmed Cys(303) as the site of glycosylation. Exposure of the glycosyl-enzyme intermediates to a disaccharide acceptor results in the formation of the corresponding enzymatic trisaccharide products. These findings suggest that the GTA(E303C) and GTB(E303C) mutants may operate by a double-displacement mechanism.
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Affiliation(s)
- Naoto Soya
- Alberta Ingenuity Centre for Carbohydrate Science, Department of Chemistry, University of Alberta, Edmonton, Alta, Canada
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Schuman B, Persson M, Landry RC, Polakowski R, Weadge JT, Seto NOL, Borisova SN, Palcic MM, Evans SV. Cysteine-to-serine mutants dramatically reorder the active site of human ABO(H) blood group B glycosyltransferase without affecting activity: structural insights into cooperative substrate binding. J Mol Biol 2010; 402:399-411. [PMID: 20655926 PMCID: PMC3069981 DOI: 10.1016/j.jmb.2010.07.036] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2010] [Revised: 07/15/2010] [Accepted: 07/18/2010] [Indexed: 11/29/2022]
Abstract
A common feature in the structures of GT-A-fold-type glycosyltransferases is a mobile polypeptide loop that has been observed to participate in substrate recognition and enclose the active site upon substrate binding. This is the case for the human ABO(H) blood group B glycosyltransferase GTB, where amino acid residues 177-195 display significantly higher levels of disorder in the unliganded state than in the fully liganded state. Structural studies of mutant enzymes GTB/C80S/C196S and GTB/C80S/C196S/C209S at resolutions ranging from 1.93 to 1.40 A display the opposite trend, where the unliganded structures show nearly complete ordering of the mobile loop residues that is lost upon substrate binding. In the liganded states of the mutant structures, while the UDP moiety of the donor molecule is observed to bind in the expected location, the galactose moiety is observed to bind in a conformation significantly different from that observed for the wild-type chimeric structures. Although this would be expected to impede catalytic turnover, the kinetics of the transfer reaction are largely unaffected. These structures demonstrate that the enzymes bind the donor in a conformation more similar to the dominant solution rotamer and facilitate its gyration into the catalytically competent form. Further, by preventing active-site closure, these structures provide a basis for recently observed cooperativity in substrate binding. Finally, the mutation of C80S introduces a fully occupied UDP binding site at the enzyme dimer interface that is observed to be dependent on the binding of H antigen acceptor analog.
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Affiliation(s)
- Brock Schuman
- Department of Biochemistry and Microbiology, University of Victoria, PO Box 3800, STN CSC, Petch Building, Victoria, BC, Canada V8W 3P6
| | - Mattias Persson
- Carlsberg Laboratory, Gamle Carlsberg Vej 10, DK-200 Valby, Denmark
| | - Roxanne C. Landry
- Department of Biochemistry, Microbiology and Immunology, University of Ottawa, 451 Smyth Road, Ottawa, Ontario, Canada K1H 8M5
| | - Robert Polakowski
- Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2G2
| | - Joel T. Weadge
- Carlsberg Laboratory, Gamle Carlsberg Vej 10, DK-200 Valby, Denmark
| | - Nina O. L. Seto
- Department of Biochemistry and Microbiology, University of Victoria, PO Box 3800, STN CSC, Petch Building, Victoria, BC, Canada V8W 3P6
- Institute for Biological Sciences, National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario, Canada K1A 0R6
| | - Svetlana N. Borisova
- Department of Biochemistry and Microbiology, University of Victoria, PO Box 3800, STN CSC, Petch Building, Victoria, BC, Canada V8W 3P6
| | - Monica M. Palcic
- Carlsberg Laboratory, Gamle Carlsberg Vej 10, DK-200 Valby, Denmark
- Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2G2
| | - Stephen V. Evans
- Department of Biochemistry and Microbiology, University of Victoria, PO Box 3800, STN CSC, Petch Building, Victoria, BC, Canada V8W 3P6
- Department of Biochemistry, Microbiology and Immunology, University of Ottawa, 451 Smyth Road, Ottawa, Ontario, Canada K1H 8M5
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Hult AK, Yazer MH, Jørgensen R, Hellberg Å, Hustinx H, Peyrard T, Palcic MM, Olsson ML. Weak A phenotypes associated with novel ABO alleles carrying the A2-related 1061C deletion and various missense substitutions. Transfusion 2010; 50:1471-86. [DOI: 10.1111/j.1537-2995.2010.02670.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Pavlicek J, Coon SL, Ganguly S, Weller JL, Hassan SA, Sackett DL, Klein DC. Evidence that proline focuses movement of the floppy loop of arylalkylamine N-acetyltransferase (EC 2.3.1.87). J Biol Chem 2008; 283:14552-8. [PMID: 18362150 PMCID: PMC2386931 DOI: 10.1074/jbc.m800593200] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2008] [Revised: 03/14/2008] [Indexed: 11/06/2022] Open
Abstract
Arylalkylamine N-acetyltransferase (AANAT) catalyzes the N-acetylation of serotonin, the penultimate step in the synthesis of melatonin. Pineal AANAT activity increases at night in all vertebrates, resulting in increased melatonin production. This increases circulating levels of melatonin, thereby providing a hormonal signal of darkness. Kinetic and structural analysis of AANAT has determined that one element is floppy. This element, termed Loop 1, is one of three loops that comprise the arylalkylamine binding pocket. During the course of chordate evolution, Loop 1 acquired the tripeptide CPL, and the enzyme became highly active. Here we focused on the functional importance of the CPL tripeptide and found that activity was markedly reduced when it was absent. Moreover, increasing the local flexibility of this tripeptide region by P64G and P64A mutations had the counterintuitive effect of reducing activity and reducing the overall movement of Loop 1, as estimated from Langevin dynamics simulations. Binding studies indicate that these mutations increased the off-rate constant of a model substrate without altering the dissociation constant. The structural kink and local rigidity imposed by Pro-64 may enhance activity by favoring configurations of Loop 1 that facilitate catalysis and do not become immobilized by intramolecular interactions.
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Affiliation(s)
- Jiri Pavlicek
- Section of Neuroendocrinology, Program on Developmental Endocrinology and Genetics, NIH, Bethesda, MD 20892, USA
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Mannerstedt K, Hindsgaul O. Synthesis and photolytic activation of 6''-O-2-nitrobenzyl uridine-5'-diphosphogalactose: a 'caged' UDP-Gal derivative. Carbohydr Res 2008; 343:875-81. [PMID: 18275942 DOI: 10.1016/j.carres.2008.01.021] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2007] [Revised: 01/14/2008] [Accepted: 01/17/2008] [Indexed: 10/22/2022]
Abstract
Placing an 2-nitrobenzyl group on O-6 of the galactosyl residue in uridine-5'-diphosphogalactose (UDP-Gal) gives 6''-O-2-nitrobenzyl-UDP-Gal that is shown to be inactive as a donor substrate for beta-(1-->4)-galactosyltransferase (GalT). On irradiation at 365 nm, the nitrobenzyl group is completely removed yielding native UDP-Gal that then transfers normally to produce the expected betaGal-(1-->4)-betaGlcNAc disaccharidic linkage. 6''-O-2-Nitrobenzyl-UDP-Gal thus fulfils the minimum requirements of a 'caged' UDP-Gal for application in time-resolved crystallographic studies of beta-(1-->4)-GalT.
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Affiliation(s)
- Karin Mannerstedt
- Carlsberg Laboratory, Gamle Carlsberg Vej 10, Valby, Copenhagen, Denmark
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Hosseini-Maaf B, Letts JA, Persson M, Smart E, LePennec PY, Hustinx H, Zhao Z, Palcic MM, Evans SV, Chester MA, Olsson ML. Structural basis for red cell phenotypic changes in newly identified, naturally occurring subgroup mutants of the human blood group B glycosyltransferase. Transfusion 2007; 47:864-75. [PMID: 17465952 DOI: 10.1111/j.1537-2995.2007.01203.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND Four amino-acid-changing polymorphisms differentiate the blood group A and B alleles. Multiple missense mutations are associated with weak expression of A and B antigens but the structural changes causing subgroups have not been studied. STUDY DESIGN AND METHODS Individuals or families having serologically weak B antigen on their red cells were studied. Alleles were characterized by sequencing of exons 1 through 7 in the ABO gene. Single crystal X-ray diffraction, three-dimensional-structure molecular modeling, and enzyme kinetics showed the effects of the B allele mutations on the glycosyltransferases. RESULTS Seven unrelated individuals with weak B phenotypes possessed seven different B alleles, five of which are new and result in substitution of highly conserved amino acids: M189V, I192T, F216I, D262N, and A268T. One of these (F216I) was due to a hybrid allele resulting from recombination between B and O(1v) alleles. The two other alleles were recently described in other ethnic groups and result in V175M and L232P. The first crystal-structure determination (A268T) of a subgroup glycosyltransferase and molecular modeling (F216I, D262N, L232P) indicated conformational changes in the enzyme that could explain the diminished enzyme activity. The effect of three mutations could not be visualized since they occur in a disordered loop. CONCLUSION The genetic background for B(w) phenotypes is very heterogeneous but usually arises through seemingly random missense mutations throughout the last ABO exon. The targeted amino acid residues, however, are well conserved during evolution. Based on analysis of the resulting structural changes in the glycosyltransferase, the mutations are likely to disrupt molecular bonds of importance for enzymatic function.
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Affiliation(s)
- Bahram Hosseini-Maaf
- Division of Hematology and Transfusion Medicine, Department of Laboratory Medicine, Lund University and Blood Center, Lund University Hospital, Lund, Sweden
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Jamaluddin H, Tumbale P, Withers SG, Acharya KR, Brew K. Conformational changes induced by binding UDP-2F-galactose to alpha-1,3 galactosyltransferase- implications for catalysis. J Mol Biol 2007; 369:1270-81. [PMID: 17493636 DOI: 10.1016/j.jmb.2007.04.012] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2007] [Revised: 04/02/2007] [Accepted: 04/03/2007] [Indexed: 11/24/2022]
Abstract
Alpha-1,3 galactosyltransferase (alpha3GT) catalyzes the transfer of galactose from UDP-galactose to beta-linked galactosides with retention of its alpha configuration. Although several complexes of alpha3GT with inhibitors and substrates have been reported, no structure has been determined of a complex containing intact UDP-galactose. We describe the structure of a complex containing an inhibitory analogue of UDP-galactose, UDP-2F-galactose, in a complex with the Arg365Lys mutant of alpha3GT. The inhibitor is bound in a distorted, bent configuration and comparison with the structure of the apo form of this mutant shows that the interaction induces structural changes in the enzyme, implying a role for ground state destabilization in catalysis. In addition to a general reduction in flexibility in the enzyme indicated by a large reduction in crystallographic B-factors, two loops, one centred around Trp195 and one encompassing the C-terminal 11 residues undergo large structural changes in complexes with UDP and UDP derivatives. The distorted configuration of the bound UDP-2F-galactose in its complex is stabilized, in part, by interactions with residues that are part of or near the flexible loops. Mutagenesis and truncation studies indicate that two highly conserved basic amino acid residues in the C-terminal region, Lys359 and Arg365 are important for catalysis, probably reflecting their roles in these ligand-mediated conformational changes. A second Mn(2+) cofactor has been identified in the catalytic site of a complex of the Arg365Lys with UDP, in a location that suggests it could play a role in facilitating UDP release, consistent with kinetic studies that show alpha3GT activity depends on the binding of two manganese ions. Conformational changes in the C-terminal 11 residues require an initial reorganization of the Trp195 loop and are linked to enzyme progress through the catalytic cycle, including donor substrate distortion, cleavage of the UDP-galactose bond, galactose transfer, and UDP release.
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Affiliation(s)
- Haryati Jamaluddin
- Department of Biology and Biochemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK
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