1
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Griffiths WA, Spencer KD, Thoden JB, Holden HM. Biochemical investigation of an N-acetyltransferase from Helicobacter pullorum. Protein Sci 2021; 30:2418-2432. [PMID: 34651380 DOI: 10.1002/pro.4207] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Revised: 10/08/2021] [Accepted: 10/12/2021] [Indexed: 11/08/2022]
Abstract
N-acetylated sugars are often found, for example, on the lipopolysaccharides of Gram-negative bacteria, on the S-layers of Gram-positive bacteria, and on the capsular polysaccharides. Key enzymes involved in their biosynthesis are the sugar N-acetyltransferases. Here, we describe a structural and functional analysis of one such enzyme from Helicobacter pullorum, an emerging pathogen that may be associated with gastroenteritis and gallbladder and liver diseases. For this analysis, the gene BA919-RS02330 putatively encoding an N-acetyltransferase was cloned, and the corresponding protein was expressed and purified. A kinetic analysis demonstrated that the enzyme utilizes dTDP-3-amino-3,6-dideoxy-d-glucose as a substrate as well as dTDP-3-amino-3,6-dideoxy-d-galactose, albeit at a reduced rate. In addition to this kinetic analysis, a similar enzyme from Helicobacter bilis was cloned and expressed, and its kinetic parameters were determined. Seven X-ray crystallographic structures of various complexes of the H. pullorum wild-type enzyme (or the C80T variant) were determined to resolutions of 1.7 Å or higher. The overall molecular architecture of the H. pullorum N-acetyltransferase places it into the Class II left-handed-β-helix superfamily (LβH). Taken together, the data presented herein suggest that 3-acetamido-3,6-dideoxy-d-glucose (or the galactose derivative) is found on either the H. pullorum O-antigen or in another of its complex glycoconjugates. A BLAST search suggests that more than 50 non-pylori Helicobacter spp. have genes encoding N-acetyltransferases. Given that there is little information concerning the complex glycans in non-pylori Helicobacter spp. and considering their zoonotic potential, our results provide new biochemical insight into these pathogens.
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Affiliation(s)
- William A Griffiths
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin, USA
| | - Keelan D Spencer
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin, USA
| | - James B Thoden
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin, USA
| | - Hazel M Holden
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin, USA
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2
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Suh CE, Carder HM, Wendlandt AE. Selective Transformations of Carbohydrates Inspired by Radical-Based Enzymatic Mechanisms. ACS Chem Biol 2021; 16:1814-1828. [PMID: 33988380 DOI: 10.1021/acschembio.1c00190] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Enzymes are a longstanding source of inspiration for synthetic reaction development. However, enzymatic reactivity and selectivity are frequently untenable in a synthetic context, as the principles that govern control in an enzymatic setting often do not translate to small molecule catalysis. Recent synthetic methods have revealed the viability of using small molecule catalysts to promote highly selective radical-mediated transformations of minimally protected sugar substrates. These transformations share conceptual similarities with radical SAM enzymes found in microbial carbohydrate biosynthesis and present opportunities for synthetic chemists to access microbial and unnatural carbohydrate building blocks without the need for protecting groups or lengthy synthetic sequences. Here, we highlight strategies through which radical reaction pathways can enable the site-, regio-, and diastereoselective transformation of minimally protected carbohydrates in both synthetic and enzymatic systems.
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Affiliation(s)
- Carolyn E. Suh
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Hayden M. Carder
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Alison E. Wendlandt
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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3
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Kappler K, Hennet T. Emergence and significance of carbohydrate-specific antibodies. Genes Immun 2020; 21:224-239. [PMID: 32753697 PMCID: PMC7449879 DOI: 10.1038/s41435-020-0105-9] [Citation(s) in RCA: 53] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Revised: 07/14/2020] [Accepted: 07/22/2020] [Indexed: 12/14/2022]
Abstract
Carbohydrate-specific antibodies are widespread among all classes of immunoglobulins. Despite their broad occurrence, little is known about their formation and biological significance. Carbohydrate-specific antibodies are often classified as natural antibodies under the assumption that they arise without prior exposure to exogenous antigens. On the other hand, various carbohydrate-specific antibodies, including antibodies to ABO blood group antigens, emerge after the contact of immune cells with the intestinal microbiota, which expresses a vast diversity of carbohydrate antigens. Here we explore the development of carbohydrate-specific antibodies in humans, addressing the definition of natural antibodies and the production of carbohydrate-specific antibodies upon antigen stimulation. We focus on the significance of the intestinal microbiota in shaping carbohydrate-specific antibodies not just in the gut, but also in the blood circulation. The structural similarity between bacterial carbohydrate antigens and surface glycoconjugates of protists, fungi and animals leads to the production of carbohydrate-specific antibodies protective against a broad range of pathogens. Mimicry between bacterial and human glycoconjugates, however, can also lead to the generation of carbohydrate-specific antibodies that cross-react with human antigens, thereby contributing to the development of autoimmune disorders.
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Affiliation(s)
| | - Thierry Hennet
- Institute of Physiology, University of Zurich, Zurich, Switzerland.
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4
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Bacterial carbohydrate diversity - a Brave New World. Curr Opin Chem Biol 2019; 53:1-8. [PMID: 31176085 DOI: 10.1016/j.cbpa.2019.04.026] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Revised: 04/29/2019] [Accepted: 04/30/2019] [Indexed: 12/11/2022]
Abstract
Glycans and glycoconjugates feature on the 'front line' of bacterial cells, playing critical roles in the mechanical and chemical stability of the microorganisms, and orchestrating interactions with the environment and all other living organisms. To negotiate such central tasks, bacterial glycomes incorporate a dizzying array of carbohydrate building blocks and non-carbohydrate modifications, which create opportunities for infinite structural variation. This review highlights some of the challenges and opportunities for the chemical biology community in the field of bacterial glycobiology.
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5
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Chen D, Fan S, Chen R, Xie K, Yin S, Sun L, Liu J, Yang L, Kong J, Yang Z, Dai J. Probing and Engineering Key Residues for Bis-C-glycosylation and Promiscuity of a C-Glycosyltransferase. ACS Catal 2018. [DOI: 10.1021/acscatal.8b00376] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Dawei Chen
- State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, 1 Xian Nong Tan Street, Beijing 100050, People’s Republic of China
| | - Shuai Fan
- Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, 1 Tian Tan Xi Li, Beijing 100050, People’s Republic of China
| | - Ridao Chen
- State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, 1 Xian Nong Tan Street, Beijing 100050, People’s Republic of China
| | - Kebo Xie
- State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, 1 Xian Nong Tan Street, Beijing 100050, People’s Republic of China
| | - Sen Yin
- State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, 1 Xian Nong Tan Street, Beijing 100050, People’s Republic of China
| | - Lili Sun
- College of Life and Environmental Sciences, Minzu University of China, 27 Zhong Guan Cun Southern Street, Beijing 100081, People’s Republic of China
| | - Jimei Liu
- State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, 1 Xian Nong Tan Street, Beijing 100050, People’s Republic of China
| | - Lin Yang
- College of Life and Environmental Sciences, Minzu University of China, 27 Zhong Guan Cun Southern Street, Beijing 100081, People’s Republic of China
| | - Jianqiang Kong
- State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, 1 Xian Nong Tan Street, Beijing 100050, People’s Republic of China
| | - Zhaoyong Yang
- Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, 1 Tian Tan Xi Li, Beijing 100050, People’s Republic of China
| | - Jungui Dai
- State Key Laboratory of Bioactive Substance and Function of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, 1 Xian Nong Tan Street, Beijing 100050, People’s Republic of China
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6
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Andreeßen C, Gerlt V, Steinbüchel A. Conversion of cysteine to 3‐mercaptopyruvic acid by bacterial aminotransferases. Enzyme Microb Technol 2017; 99:38-48. [DOI: 10.1016/j.enzmictec.2017.01.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2016] [Revised: 12/27/2016] [Accepted: 01/11/2017] [Indexed: 10/20/2022]
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7
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Dow GT, Gilbert M, Thoden JB, Holden HM. Structural investigation on WlaRG from Campylobacter jejuni: A sugar aminotransferase. Protein Sci 2017; 26:586-599. [PMID: 28028852 DOI: 10.1002/pro.3109] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2016] [Accepted: 12/22/2016] [Indexed: 12/12/2022]
Abstract
Campylobacter jejuni is a Gram-negative bacterium that represents a leading cause of human gastroenteritis worldwide. Of particular concern is the link between C. jejuni infections and the subsequent development of Guillain-Barré syndrome, an acquired autoimmune disorder leading to paralysis. All Gram-negative bacteria contain complex glycoconjugates anchored to their outer membranes, but in most strains of C. jejuni, this lipoglycan lacks the O-antigen repeating units. Recent mass spectrometry analyses indicate that the C. jejuni 81116 (Penner serotype HS:6) lipoglycan contains two dideoxyhexosamine residues, and enzymological assay data show that this bacterial strain can synthesize both dTDP-3-acetamido-3,6-dideoxy-d-glucose and dTDP-3-acetamido-3,6-dideoxy-d-galactose. The focus of this investigation is on WlaRG from C. jejuni, which plays a key role in the production of these unusual sugars by functioning as a pyridoxal 5'-phosphate dependent aminotransferase. Here, we describe the first three-dimensional structures of the enzyme in various complexes determined to resolutions of 1.7 Å or higher. Of particular significance are the external aldimine structures of WlaRG solved in the presence of either dTDP-3-amino-3,6-dideoxy-d-galactose or dTDP-3-amino-3,6-dideoxy-d-glucose. These models highlight the manner in which WlaRG can accommodate sugars with differing stereochemistries about their C-4' carbon positions. In addition, we present a corrected structure of WbpE, a related sugar aminotransferase from Pseudomonas aeruginosa, solved to 1.3 Å resolution.
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Affiliation(s)
- Garrett T Dow
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin, 53706
| | - Michel Gilbert
- National Research Council Canada, Human Health Therapeutics, Ottawa, Ontario, K1A 0R6, Canada
| | - James B Thoden
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin, 53706
| | - Hazel M Holden
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin, 53706
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8
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Zhu JS, McCormick NE, Timmons SC, Jakeman DL. Synthesis of α-Deoxymono and Difluorohexopyranosyl 1-Phosphates and Kinetic Evaluation with Thymidylyl- and Guanidylyltransferases. J Org Chem 2016; 81:8816-8825. [DOI: 10.1021/acs.joc.6b01485] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Jian-She Zhu
- College
of Pharmacy, Dalhousie University, 5968 College Street, Halifax, Nova Scotia B3H 3J5, Canada
| | - Nicole E. McCormick
- College
of Pharmacy, Dalhousie University, 5968 College Street, Halifax, Nova Scotia B3H 3J5, Canada
| | - Shannon C. Timmons
- Department
of Chemistry, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
| | - David L. Jakeman
- College
of Pharmacy, Dalhousie University, 5968 College Street, Halifax, Nova Scotia B3H 3J5, Canada
- Department
of Chemistry, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
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9
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Zachman-Brockmeyer TR, Thoden JB, Holden HM. Structures of KdnB and KdnA from Shewanella oneidensis: Key Enzymes in the Formation of 8-Amino-3,8-Dideoxy-d-Manno-Octulosonic Acid. Biochemistry 2016; 55:4485-94. [PMID: 27275764 DOI: 10.1021/acs.biochem.6b00439] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
8-Amino-3,8-dideoxy-d-manno-octulosonic acid (Kdo8N) is a unique amino sugar that has thus far only been observed on the lipopolysaccharides of marine bacteria belonging to the genus Shewanella. Although its biological function is still unclear, it is thought that the sugar is important for the integrity of the bacterial cell outer membrane. A three-gene cluster required for the biosynthesis of Kdo8N was first identified in Shewanella oneidensis. Here we describe the three-dimensional structures of two of the enzymes required for Kdo8N biosynthesis in S. oneidensis, namely, KdnB and KdnA. The structure of KdnB was solved to 1.85-Å resolution, and its overall three-dimensional architecture places it into the Group III alcohol dehydrogenase superfamily. A previous study suggested that KdnB did not require NAD(P) for activity. Strikingly, although the protein was crystallized in the absence of any cofactors, the electron density map clearly revealed the presence of a tightly bound NAD(H). In addition, a bound metal was observed, which was shown via X-ray fluorescence to be a zinc ion. Unlike other members of the Group III alcohol dehydrogenases, the dinucleotide cofactor in KdnB is tightly bound and cannot be removed without leading to protein precipitation. With respect to KdnA, it is a pyridoxal 5'-phosphate or (PLP)-dependent aminotransferase. For this analysis, the structure of KdnA, trapped in the presence of the external aldimine with PLP and glutamate, was determined to 2.15-Å resolution. The model of KdnA represents the first structure of a sugar aminotransferase that functions on an 8-oxo sugar. Taken together the results reported herein provide new molecular insight into the biosynthesis of Kdo8N.
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Affiliation(s)
| | - James B Thoden
- Department of Biochemistry, University of Wisconsin , Madison, Wisconsin 53706, United States
| | - Hazel M Holden
- Department of Biochemistry, University of Wisconsin , Madison, Wisconsin 53706, United States
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10
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Riegert AS, Young NM, Watson DC, Thoden JB, Holden HM. Structure of the external aldimine form of PglE, an aminotransferase required for N,N'-diacetylbacillosamine biosynthesis. Protein Sci 2015; 24:1609-16. [PMID: 26178292 DOI: 10.1002/pro.2745] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2015] [Accepted: 06/30/2015] [Indexed: 12/23/2022]
Abstract
N,N'-diacetylbacillosamine is a novel sugar that plays a key role in bacterial glycosylation. Three enzymes are required for its biosynthesis in Campylobacter jejuni starting from UDP-GlcNAc. The focus of this investigation, PglE, catalyzes the second step in the pathway. It is a PLP-dependent aminotransferase that converts UDP-2-acetamido-4-keto-2,4,6-trideoxy-d-glucose to UDP-2-acetamido-4-amino-2,4,6-trideoxy-d-glucose. For this investigation, the structure of PglE in complex with an external aldimine was determined to a nominal resolution of 2.0 Å. A comparison of its structure with those of other sugar aminotransferases reveals a remarkable difference in the manner by which PglE accommodates its nucleotide-linked sugar substrate.
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Affiliation(s)
- Alexander S Riegert
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin, 53706
| | - N Martin Young
- Human Health Therapeutics, National Research Council Canada, Ottawa, Ontario, Canada, K1A OR6
| | - David C Watson
- Human Health Therapeutics, National Research Council Canada, Ottawa, Ontario, Canada, K1A OR6
| | - James B Thoden
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin, 53706
| | - Hazel M Holden
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin, 53706
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11
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De Bruyn F, Maertens J, Beauprez J, Soetaert W, De Mey M. Biotechnological advances in UDP-sugar based glycosylation of small molecules. Biotechnol Adv 2015; 33:288-302. [PMID: 25698505 DOI: 10.1016/j.biotechadv.2015.02.005] [Citation(s) in RCA: 113] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2014] [Revised: 12/19/2014] [Accepted: 02/09/2015] [Indexed: 01/04/2023]
Abstract
Glycosylation of small molecules like specialized (secondary) metabolites has a profound impact on their solubility, stability or bioactivity, making glycosides attractive compounds as food additives, therapeutics or nutraceuticals. The subsequently growing market demand has fuelled the development of various biotechnological processes, which can be divided in the in vitro (using enzymes) or in vivo (using whole cells) production of glycosides. In this context, uridine glycosyltransferases (UGTs) have emerged as promising catalysts for the regio- and stereoselective glycosylation of various small molecules, hereby using uridine diphosphate (UDP) sugars as activated glycosyldonors. This review gives an extensive overview of the recently developed in vivo production processes using UGTs and discusses the major routes towards UDP-sugar formation. Furthermore, the use of interconverting enzymes and glycorandomization is highlighted for the production of unusual or new-to-nature glycosides. Finally, the technological challenges and future trends in UDP-sugar based glycosylation are critically evaluated and summarized.
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Affiliation(s)
- Frederik De Bruyn
- Centre of Expertise-Industrial Biotechnology and Biocatalysis, Department of Biochemical and Microbial Technology, Ghent University, Coupure links 653, 9000 Ghent, Belgium
| | - Jo Maertens
- Centre of Expertise-Industrial Biotechnology and Biocatalysis, Department of Biochemical and Microbial Technology, Ghent University, Coupure links 653, 9000 Ghent, Belgium
| | - Joeri Beauprez
- Centre of Expertise-Industrial Biotechnology and Biocatalysis, Department of Biochemical and Microbial Technology, Ghent University, Coupure links 653, 9000 Ghent, Belgium
| | - Wim Soetaert
- Centre of Expertise-Industrial Biotechnology and Biocatalysis, Department of Biochemical and Microbial Technology, Ghent University, Coupure links 653, 9000 Ghent, Belgium
| | - Marjan De Mey
- Centre of Expertise-Industrial Biotechnology and Biocatalysis, Department of Biochemical and Microbial Technology, Ghent University, Coupure links 653, 9000 Ghent, Belgium.
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12
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Chantigian DP, Thoden JB, Holden HM. Structural and biochemical characterization of a bifunctional ketoisomerase/N-acetyltransferase from Shewanella denitrificans. Biochemistry 2013; 52:8374-85. [PMID: 24128043 DOI: 10.1021/bi401170t] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Unusual N-acetylated sugars have been observed on the O-antigens of some Gram-negative bacteria and on the S-layers of both Gram-positive and Gram-negative bacteria. One such sugar is 3-acetamido-3,6-dideoxy-α-d-galactose or Fuc3NAc. The pathway for its production requires five enzymes with the first step involving the attachment of dTMP to glucose-1-phosphate. Here, we report a structural and biochemical characterization of a bifunctional enzyme from Shewanella denitificans thought to be involved in the biosynthesis of dTDP-Fuc3NAc. On the basis of a bioinformatics analysis, the enzyme, hereafter referred to as FdtD, has been postulated to catalyze the third and fifth steps in the pathway, namely, a 3,4-keto isomerization and an N-acetyltransferase reaction. For the X-ray analysis reported here, the enzyme was crystallized in the presence of dTDP and CoA. The crystal structure shows that FdtD adopts a hexameric quaternary structure with 322 symmetry. Each subunit of the hexamer folds into two distinct domains connected by a flexible loop. The N-terminal domain adopts a left-handed β-helix motif and is responsible for the N-acetylation reaction. The C-terminal domain folds into an antiparallel flattened β-barrel that harbors the active site responsible for the isomerization reaction. Biochemical assays verify the two proposed catalytic activities of the enzyme and reveal that the 3,4-keto isomerization event leads to the inversion of configuration about the hexose C-4' carbon.
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Affiliation(s)
- Daniel P Chantigian
- Department of Biochemistry, University of Wisconsin , Madison, Wisconsin 53706, United States
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13
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Metsä-Ketelä M, Oja T, Taguchi T, Okamoto S, Ichinose K. Biosynthesis of pyranonaphthoquinone polyketides reveals diverse strategies for enzymatic carbon–carbon bond formation. Curr Opin Chem Biol 2013; 17:562-70. [DOI: 10.1016/j.cbpa.2013.06.032] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2013] [Revised: 05/30/2013] [Accepted: 06/25/2013] [Indexed: 11/26/2022]
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14
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Singh S, Phillips GN, Thorson JS. The structural biology of enzymes involved in natural product glycosylation. Nat Prod Rep 2012; 29:1201-37. [PMID: 22688446 DOI: 10.1039/c2np20039b] [Citation(s) in RCA: 89] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The glycosylation of microbial natural products often dramatically influences the biological and/or pharmacological activities of the parental metabolite. Over the past decade, crystal structures of several enzymes involved in the biosynthesis and attachment of novel sugars found appended to natural products have emerged. In many cases, these studies have paved the way to a better understanding of the corresponding enzyme mechanism of action and have served as a starting point for engineering variant enzymes to facilitate to production of differentially-glycosylated natural products. This review specifically summarizes the structural studies of bacterial enzymes involved in biosynthesis of novel sugar nucleotides.
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Affiliation(s)
- Shanteri Singh
- Laboratory for Biosynthetic Chemistry, Pharmaceutical Sciences Division, School of Pharmacy, University of Wisconsin-Madison, 777 Highland Avenue, Madison, WI 53705, USA
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15
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Thoden JB, Reinhardt LA, Cook PD, Menden P, Cleland WW, Holden HM. Catalytic mechanism of perosamine N-acetyltransferase revealed by high-resolution X-ray crystallographic studies and kinetic analyses. Biochemistry 2012; 51:3433-44. [PMID: 22443398 DOI: 10.1021/bi300197h] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
N-Acetylperosamine is an unusual dideoxysugar found in the O-antigens of some Gram-negative bacteria, including the pathogenic Escherichia coli strain O157:H7. The last step in its biosynthesis is catalyzed by PerB, an N-acetyltransferase belonging to the left-handed β-helix superfamily of proteins. Here we describe a combined structural and functional investigation of PerB from Caulobacter crescentus. For this study, three structures were determined to 1.0 Å resolution or better: the enzyme in complex with CoA and GDP-perosamine, the protein with bound CoA and GDP-N-acetylperosamine, and the enzyme containing a tetrahedral transition state mimic bound in the active site. Each subunit of the trimeric enzyme folds into two distinct regions. The N-terminal domain is globular and dominated by a six-stranded mainly parallel β-sheet. It provides most of the interactions between the protein and GDP-perosamine. The C-terminal domain consists of a left-handed β-helix, which has nearly seven turns. This region provides the scaffold for CoA binding. On the basis of these high-resolution structures, site-directed mutant proteins were constructed to test the roles of His 141 and Asp 142 in the catalytic mechanism. Kinetic data and pH-rate profiles are indicative of His 141 serving as a general base. In addition, the backbone amide group of Gly 159 provides an oxyanion hole for stabilization of the tetrahedral transition state. The pH-rate profiles are also consistent with the GDP-linked amino sugar substrate entering the active site in its unprotonated form. Finally, for this investigation, we show that PerB can accept GDP-3-deoxyperosamine as an alternative substrate, thus representing the production of a novel trideoxysugar.
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Affiliation(s)
- James B Thoden
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706, USA
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16
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Romo AJ, Liu HW. Mechanisms and structures of vitamin B(6)-dependent enzymes involved in deoxy sugar biosynthesis. BIOCHIMICA ET BIOPHYSICA ACTA 2011; 1814:1534-47. [PMID: 21315852 PMCID: PMC3115481 DOI: 10.1016/j.bbapap.2011.02.003] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2010] [Revised: 01/08/2011] [Accepted: 02/01/2011] [Indexed: 10/18/2022]
Abstract
PLP is well-regarded for its role as a coenzyme in a number of diverse enzymatic reactions. Transamination, deoxygenation, and aldol reactions mediated by PLP-dependent enzymes enliven and enrich deoxy sugar biosynthesis, endowing these compounds with unique structures and contributing to their roles as determinants of biological activity in many natural products. The importance of deoxy aminosugars in natural product biosynthesis has spurred several recent structural investigations of sugar aminotransferases. The structure of a PMP-dependent enzyme catalyzing the C-3 deoxygenation reaction in the biosynthesis of ascarylose was also determined. These studies, and the crystal structures they have provided, offer a wealth of new insights regarding the enzymology of PLP/PMP-dependent enzymes in deoxy sugar biosynthesis. In this review, we consider these recent achievements in the structural biology of deoxy sugar biosynthetic enzymes and the important implications they hold for understanding enzyme catalysis and natural product biosynthesis in general. This article is part of a Special Issue entitled: Pyridoxal Phosphate Enzymology.
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Affiliation(s)
- Anthony J. Romo
- Division of Medicinal Chemistry, College of Pharmacy, and Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas 78712
| | - Hung-wen Liu
- Division of Medicinal Chemistry, College of Pharmacy, and Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas 78712
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17
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Kubiak RL, Holden HM. Combined structural and functional investigation of a C-3''-ketoreductase involved in the biosynthesis of dTDP-L-digitoxose. Biochemistry 2011; 50:5905-17. [PMID: 21598943 DOI: 10.1021/bi200514b] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
l-Digitoxose is an unusual dideoxysugar found attached to various pharmacologically active natural products, including the antitumor antibiotic tetrocarcin A and the antibiotics kijanimicin and jadomycin B. Six enzymes are required for its production starting from glucose 1-phosphate. Here we describe a combined structural and functional investigation of KijD10, an NADPH-dependent C-3''-ketoreductase that catalyzes the third step of l-digitoxose biosynthesis in the African soil-dwelling bacterium Actinomadura kijaniata. KijD10 belongs to the glucose-fructose oxidoreductase superfamily. For this investigation, both binary and ternary complexes of KijD10 were crystallized, and their structures were determined to 2.0 Å resolution or better. On the basis of these high-resolution structures, two potential active site acids were identified, Lys 102 and Tyr 186. These residues were individually mutated and the resultant proteins investigated both kinetically and structurally. The Y186F mutant protein demonstrated significant catalytic activity, and its structure was virtually identical to that of the wild-type enzyme except for the positioning of the nicotinamide ring. All lysine mutations, on the other hand, resulted in proteins with either abolished or drastically reduced catalytic activities. Structures for the K102A and K102E mutant proteins were determined and showed that the abrogation of catalytic activity was not a result of large conformational changes. Taken together, these data suggest that Lys 102 donates a proton to the C-3'' keto group during the reaction and that Tyr 186 serves only an auxiliary role. This is in contrast to that proposed for glucose-fructose oxidoreductase and other family members in which the tyrosines, or in some cases similarly positioned histidines, are thought to play major catalytic roles.
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Affiliation(s)
- Rachel L Kubiak
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706, United States
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Larkin A, Imperiali B. The expanding horizons of asparagine-linked glycosylation. Biochemistry 2011; 50:4411-26. [PMID: 21506607 DOI: 10.1021/bi200346n] [Citation(s) in RCA: 176] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Asparagine-linked glycosylation involves the sequential assembly of an oligosaccharide onto a polyisoprenyl donor, followed by the en bloc transfer of the glycan to particular asparagine residues within acceptor proteins. These N-linked glycans play a critical role in a wide variety of biological processes, such as protein folding, cellular targeting and motility, and the immune response. In the past decade, research in the field of N-linked glycosylation has achieved major advances, including the discovery of new carbohydrate modifications, the biochemical characterization of the enzymes involved in glycan assembly, and the determination of the biological impact of these glycans on target proteins. It is now firmly established that this enzyme-catalyzed modification occurs in all three domains of life. However, despite similarities in the overall logic of N-linked glycoprotein biosynthesis among the three kingdoms, the structures of the appended glycans are markedly different and thus influence the functions of elaborated proteins in various ways. Though nearly all eukaryotes produce the same nascent tetradecasaccharide (Glc(3)Man(9)GlcNAc(2)), heterogeneity is introduced into this glycan structure after it is transferred to the protein through a complex series of glycosyl trimming and addition steps. In contrast, bacteria and archaea display diversity within their N-linked glycan structures through the use of unique monosaccharide building blocks during the assembly process. In this review, recent progress toward gaining a deeper biochemical understanding of this modification across all three kingdoms will be summarized. In addition, a brief overview of the role of N-linked glycosylation in viruses will also be presented.
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Affiliation(s)
- Angelyn Larkin
- Department of Chemistry Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
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