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Anderson AC, Stangherlin S, Pimentel KN, Weadge JT, Clarke AJ. The SGNH hydrolase family: a template for carbohydrate diversity. Glycobiology 2022; 32:826-848. [PMID: 35871440 PMCID: PMC9487903 DOI: 10.1093/glycob/cwac045] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2022] [Revised: 06/20/2022] [Accepted: 07/05/2022] [Indexed: 11/14/2022] Open
Abstract
The substitution and de-substitution of carbohydrate materials are important steps in the biosynthesis and/or breakdown of a wide variety of biologically important polymers. The SGNH hydrolase superfamily is a group of related and well-studied proteins with a highly conserved catalytic fold and mechanism composed of 16 member families. SGNH hydrolases can be found in vertebrates, plants, fungi, bacteria, and archaea, and play a variety of important biological roles related to biomass conversion, pathogenesis, and cell signaling. The SGNH hydrolase superfamily is chiefly composed of a diverse range of carbohydrate-modifying enzymes, including but not limited to the carbohydrate esterase families 2, 3, 6, 12 and 17 under the carbohydrate-active enzyme classification system and database (CAZy.org). In this review, we summarize the structural and functional features that delineate these subfamilies of SGNH hydrolases, and which generate the wide variety of substrate preferences and enzymatic activities observed of these proteins to date.
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Affiliation(s)
- Alexander C Anderson
- Department of Molecular and Cellular Biology, University of Guelph, Guelph N1G2W1, Canada
| | - Stefen Stangherlin
- Department of Chemistry & Biochemistry, Wilfrid Laurier University, Waterloo N2L3C5, Canada
| | - Kyle N Pimentel
- Department of Molecular and Cellular Biology, University of Guelph, Guelph N1G2W1, Canada
| | - Joel T Weadge
- Department of Biology, Wilfrid Laurier University, Waterloo N2L3C5, Canada
| | - Anthony J Clarke
- Department of Molecular and Cellular Biology, University of Guelph, Guelph N1G2W1, Canada
- Department of Chemistry & Biochemistry, Wilfrid Laurier University, Waterloo N2L3C5, Canada
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2
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Urbániková Ľ. CE16 acetylesterases: in silico analysis, catalytic machinery prediction and comparison with related SGNH hydrolases. 3 Biotech 2021; 11:84. [PMID: 33505839 DOI: 10.1007/s13205-020-02575-w] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Accepted: 12/01/2020] [Indexed: 01/23/2023] Open
Abstract
Bioinformatics analysis was focused on unique acetylesterases annotated in the CAZy database within the CE16 family and simultaneously belonging to the SGNH hydrolase superfamily. The CE16 acetylesterases were compared to structurally related SGNH hydrolases: (i) selected members of the CE2, CE3, CE6, CE12 and CE17 family of the CAZy database and (ii) structural representatives of the Lipase_GDSL and Lipase_GDSL_2 families according to the Pfam database. Sequence alignment based on four conserved sequence regions (CSRs) containing active-site residues was used to calculate sequence logos specific for each CE family and to construct a phylogenetic tree. In many members of the CE16 family, aspartic acid from the Ser-His-Asp catalytic triad has been replaced by asparagine, and based on structure-sequence comparison, an alternative catalytic dyad mechanism was predicted for these enzymes. In addition to four conserved regions, CSR-I, CSR-II, CSR-III and CSR-V, containing catalytic and oxyanion-hole residues, CSR-IV was found in the CE16 family as the only CAZy family. Tertiary structures of the characterized CE16 members prepared by homology modeling showed that the α/β/α sandwich fold as well as the topology of their active sites are preserved. The phylogenetic tree and sequence alignment indicate the existence of a subfamily in the CE16 family fully consistent with the known biochemical data. In addition, nonstandard CE16 members that differ from others were analyzed and their active-site residues were predicted. A better understanding of the structure-function relationship of acetylesterases can help in the targeted design of these enzymes for biotechnology. SUPPLEMENTARY INFORMATION The online version contains supplementary material available at 10.1007/s13205-020-02575-w.
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Jones CS, Sychantha D, Howell PL, Clarke AJ. Structural basis for the O-acetyltransferase function of the extracytoplasmic domain of OatA from Staphylococcus aureus. J Biol Chem 2020; 295:8204-8213. [PMID: 32350117 DOI: 10.1074/jbc.ra120.013108] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Revised: 04/27/2020] [Indexed: 02/03/2023] Open
Abstract
Many bacteria possess enzymes that modify the essential cell-wall polymer peptidoglycan by O-acetylation. This modification occurs in numerous Gram-positive pathogens, including methicillin-resistant Staphylococcus aureus, a common cause of human infections. O-Acetylation of peptidoglycan protects bacteria from the lytic activity of lysozyme, a mammalian innate immune enzyme, and as such is important for bacterial virulence. The O-acetylating enzyme in Gram-positive bacteria, O-acetyltransferase A (OatA), is a two-domain protein consisting of an N-terminal integral membrane domain and a C-terminal extracytoplasmic domain. Here, we present the X-ray crystal structure at 1.71 Å resolution and the biochemical characterization of the C-terminal domain of S. aureus OatA. The structure revealed that this OatA domain adopts an SGNH-hydrolase fold and possesses a canonical catalytic triad. Site-specific replacement of active-site amino acids revealed the presence of a water-coordinating aspartate residue that limits esterase activity. This residue, although conserved in staphyloccocal OatA and most other homologs, is not present in the previously characterized streptococcal OatA. These results provide insights into the mechanism of acetyl transfer in the SGNH/GDSL hydrolase family and highlight important evolutionary differences between homologous OatA enzymes. Furthermore, this study enhances our understanding of PG O-acetyltransferases, which could guide the development of novel antibacterial drugs to combat infections with multidrug-resistant bacterial pathogens.
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Affiliation(s)
- Carys S Jones
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
| | - David Sychantha
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
| | - P Lynne Howell
- Program in Molecular Medicine, The Hospital for Sick Children, Toronto, Ontario, Canada.,Department of Biochemistry, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Anthony J Clarke
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada .,Department of Chemistry and Biochemistry, Wilfrid Laurier University, Waterloo, Ontario, Canada
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A pair of esterases from a commensal gut bacterium remove acetylations from all positions on complex β-mannans. Proc Natl Acad Sci U S A 2020; 117:7122-7130. [PMID: 32170022 DOI: 10.1073/pnas.1915376117] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
β-mannans and xylans are important components of the plant cell wall and they are acetylated to be protected from degradation by glycoside hydrolases. β-mannans are widely present in human and animal diets as fiber from leguminous plants and as thickeners and stabilizers in processed foods. There are many fully characterized acetylxylan esterases (AcXEs); however, the enzymes deacetylating mannans are less understood. Here we present two carbohydrate esterases, RiCE2 and RiCE17, from the Firmicute Roseburia intestinalis, which together deacetylate complex galactoglucomannan (GGM). The three-dimensional (3D) structure of RiCE17 with a mannopentaose in the active site shows that the CBM35 domain of RiCE17 forms a confined complex, where the axially oriented C2-hydroxyl of a mannose residue points toward the Ser41 of the catalytic triad. Cavities on the RiCE17 surface may accept galactosylations at the C6 positions of mannose adjacent to the mannose residue being deacetylated (subsite -1 and +1). In-depth characterization of the two enzymes using time-resolved NMR, high-performance liquid chromatography (HPLC), and mass spectrometry demonstrates that they work in a complementary manner. RiCE17 exclusively removes the axially oriented 2-O-acetylations on any mannose residue in an oligosaccharide, including double acetylated mannoses, while the RiCE2 is active on 3-O-, 4-O-, and 6-O-acetylations. Activity of RiCE2 is dependent on RiCE17 removing 2-O-acetylations from double acetylated mannose. Furthermore, transacetylation of oligosaccharides with the 2-O-specific RiCE17 provided insight into how temperature and pH affects acetyl migration on manno-oligosaccharides.
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A novel enantioselective SGNH family esterase (NmSGNH1) from Neisseria meningitides: Characterization, mutational analysis, and ester synthesis. Biochim Biophys Acta Mol Cell Biol Lipids 2019; 1864:1438-1448. [DOI: 10.1016/j.bbalip.2019.07.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Revised: 07/10/2019] [Accepted: 07/13/2019] [Indexed: 11/18/2022]
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Brott AS, Jones CS, Clarke AJ. Development of a High Throughput Screen for the Identification of Inhibitors of Peptidoglycan O-Acetyltransferases, New Potential Antibacterial Targets. Antibiotics (Basel) 2019; 8:E65. [PMID: 31137799 PMCID: PMC6627197 DOI: 10.3390/antibiotics8020065] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Revised: 05/22/2019] [Accepted: 05/22/2019] [Indexed: 12/02/2022] Open
Abstract
The O-acetylation of peptidoglycan occurs in many Gram-negative and most Gram-positive pathogens and this modification to the essential wall polymer controls the lytic activity of the autolysins, particularly the lytic transglycosylases, and inhibits that of the lysozymes of innate immunity systems. As such, the peptidoglycan O-acetyltransferases PatA/B and OatA are recognized as virulence factors. In this study, we present the high throughput screening of small compound libraries to identify the first known inhibitors of these enzymes. The fluorometric screening assay developed involved monitoring the respective O-acetyltransferases as esterases using 4-methylumbelliferylacetate as substrate. Pilot screens of 3921 compounds validated the usefulness of the HTS protocol. A number of potential inhibitors were identified amongst a total of 145,000 low molecular-weight compounds, some of which were common to both enzymes, while others were unique to each. After eliminating a number of false positives in secondary screens, dose response curves confirmed the apparent specificity of a benzothiazolyl-pyrazolo-pyridine as an inhibitor of Neisseria gonorrhoeae PatB, and several coumarin-based compounds as inhibitors of both this PatB and OatA from Staphylococcus aureus. The benzothiazolyl-pyrazolo-pyridine was determined to be a non-competitive inhibitor of PatB with a Ki of 126 µM. At 177 µg/mL and close to its solubility limit, this compound caused a 90% reduction in growth of N. gonorrhoeae, while growth of Escherichia coli, a bacterium that lacks PatB and, hence, does not produce O-acetylated peptidoglycan, was unaffected. These data provide preliminary proof of concept that peptidoglycan O-acetyltransferases would serve as useful antibacterial targets.
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Affiliation(s)
- Ashley S Brott
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada.
| | - Carys S Jones
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada.
| | - Anthony J Clarke
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada.
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Sychantha D, Brott AS, Jones CS, Clarke AJ. Mechanistic Pathways for Peptidoglycan O-Acetylation and De-O-Acetylation. Front Microbiol 2018; 9:2332. [PMID: 30327644 PMCID: PMC6174289 DOI: 10.3389/fmicb.2018.02332] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2018] [Accepted: 09/11/2018] [Indexed: 12/22/2022] Open
Abstract
The post-synthetic O-acetylation of the essential component of bacterial cell walls, peptidoglycan (PG), is performed by many pathogenic bacteria to help them evade the lytic action of innate immunity responses. Occurring at the C-6 hydroxyl of N-acetylmuramoyl residues, this modification to the glycan backbone of PG sterically blocks the activity of lysozymes. As such, the enzyme responsible for this modification in Gram-positive bacteria is recognized as a virulence factor. With Gram-negative bacteria, the O-acetylation of PG provides a means of control of their autolysins at the substrate level. In this review, we discuss the pathways for PG O-acetylation and de-O-acetylation and the structure and function relationship of the O-acetyltransferases and O-acetylesterases that catalyze these reactions. The current understanding of their mechanisms of action is presented and the prospects of targeting these systems for the development of novel therapeutics are explored.
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Affiliation(s)
| | | | | | - Anthony J. Clarke
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, Canada
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In vitro characterization of the antivirulence target of Gram-positive pathogens, peptidoglycan O-acetyltransferase A (OatA). PLoS Pathog 2017; 13:e1006667. [PMID: 29077761 PMCID: PMC5697884 DOI: 10.1371/journal.ppat.1006667] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Revised: 11/21/2017] [Accepted: 09/25/2017] [Indexed: 12/17/2022] Open
Abstract
The O-acetylation of the essential cell wall polymer peptidoglycan occurs in most Gram-positive bacterial pathogens, including species of Staphylococcus, Streptococcus and Enterococcus. This modification to peptidoglycan protects these pathogens from the lytic action of the lysozymes of innate immunity systems and, as such, is recognized as a virulence factor. The key enzyme involved, peptidoglycan O-acetyltransferase A (OatA) represents a particular challenge to biochemical study since it is a membrane associated protein whose substrate is the insoluble peptidoglycan cell wall polymer. OatA is predicted to be bimodular, being comprised of an N-terminal integral membrane domain linked to a C-terminal extracytoplasmic domain. We present herein the first biochemical and kinetic characterization of the C-terminal catalytic domain of OatA from two important human pathogens, Staphylococcus aureus and Streptococcus pneumoniae. Using both pseudosubstrates and novel biosynthetically-prepared peptidoglycan polymers, we characterized distinct substrate specificities for the two enzymes. In addition, the high resolution crystal structure of the C-terminal domain reveals an SGNH/GDSL-like hydrolase fold with a catalytic triad of amino acids but with a non-canonical oxyanion hole structure. Site-specific replacements confirmed the identity of the catalytic and oxyanion hole residues. A model is presented for the O-acetylation of peptidoglycan whereby the translocation of acetyl groups from a cytoplasmic source across the cytoplasmic membrane is catalyzed by the N-terminal domain of OatA for their transfer to peptidoglycan by its C-terminal domain. This study on the structure-function relationship of OatA provides a molecular and mechanistic understanding of this bacterial resistance mechanism opening the prospect for novel chemotherapeutic exploration to enhance innate immunity protection against Gram-positive pathogens. Multi-drug resistance amongst important human pathogens, such as methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus (VRE) and drug-resistant Streptococcus pneumoniae (DRSP), continues to challenge clinicians and threaten the lives of infected patients. Of the several approaches being taken to address this serious issue is the development of antagonists that render the bacterial infection more susceptible to the defensive enzymes and proteins of our innate immunity systems. One such target is the enzyme O-acetyltransferase A (OatA). This extracellular enzyme modifies the essential bacterial cell wall component peptidoglycan and thereby makes it resistant to the lytic action of lysozyme, our first line of defense against invading pathogens. In this study, we present the first biochemical and structural characterization of OatA. Using both the S. aureus and S. pneumoniae enzymes as model systems, we demonstrate that OatA has unique substrate specificities. We also show that the catalytic domain of OatA is a structural homolog of a well-studied superfamily of hydrolases. It uses a catalytic triad of Ser-His-Asp to transfer acetyl groups specifically to the C-6 hydroxyl group of muramoyl residues within peptidoglycan. This information on the structure and function relationship of OatA is important for the future development of effective inhibitors which may serve as antivirulence agents.
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Uechi K, Kamachi S, Akita H, Mine S, Watanabe M. Crystal structure of an acetyl esterase complexed with acetate ion provides insights into the catalytic mechanism. Biochem Biophys Res Commun 2016; 477:383-7. [PMID: 27329813 PMCID: PMC7092896 DOI: 10.1016/j.bbrc.2016.06.093] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Accepted: 06/18/2016] [Indexed: 01/07/2023]
Abstract
We previously reported the crystal structure of an acetyl esterase (TcAE206) belonging to carbohydrate esterase family 3 from Talaromyces cellulolyticus. In this study, we solved the crystal structure of an S10A mutant of TcAE206 complexed with an acetate ion. The acetate ion was stabilized by three hydrogen bonds in the oxyanion hole instead of a water molecule as in the structure of wild-type TcAE206. Furthermore, the catalytic triad residue His182 moved 0.8 Å toward the acetate ion upon substrate entering the active site, suggesting that this movement is necessary for completion of the catalytic reaction.
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Affiliation(s)
- Keiko Uechi
- Research Institute for Sustainable Chemistry, National Institute of Advanced Industrial Science and Technology (AIST), 3-11-32 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-0046, Japan
| | - Saori Kamachi
- Research Institute for Sustainable Chemistry, National Institute of Advanced Industrial Science and Technology (AIST), 3-11-32 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-0046, Japan
| | - Hironaga Akita
- Research Institute for Sustainable Chemistry, National Institute of Advanced Industrial Science and Technology (AIST), 3-11-32 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-0046, Japan
| | - Shouhei Mine
- Biomedical Research Institute (BMD), National Institute of Advanced Industrial Science and Technology (AIST), 1-8-31 Midorigaoka, Ikeda, Osaka, 563-8577, Japan
| | - Masahiro Watanabe
- Research Institute for Sustainable Chemistry, National Institute of Advanced Industrial Science and Technology (AIST), 3-11-32 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-0046, Japan,Corresponding author. Tel.: +81 82 420 8285; fax: +81 82 423 7820.
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Ha R, Frirdich E, Sychantha D, Biboy J, Taveirne ME, Johnson JG, DiRita VJ, Vollmer W, Clarke AJ, Gaynor EC. Accumulation of Peptidoglycan O-Acetylation Leads to Altered Cell Wall Biochemistry and Negatively Impacts Pathogenesis Factors of Campylobacter jejuni. J Biol Chem 2016; 291:22686-22702. [PMID: 27474744 PMCID: PMC5077204 DOI: 10.1074/jbc.m116.746404] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Indexed: 12/30/2022] Open
Abstract
Campylobacter jejuni is a leading cause of bacterial gastroenteritis in the developed world. Despite its prevalence, its mechanisms of pathogenesis are poorly understood. Peptidoglycan (PG) is important for helical shape, colonization, and host-pathogen interactions in C. jejuni Therefore, changes in PG greatly impact the physiology of this organism. O-acetylation of peptidoglycan (OAP) is a bacterial phenomenon proposed to be important for proper cell growth, characterized by acetylation of the C6 hydroxyl group of N-acetylmuramic acid in the PG glycan backbone. The OAP gene cluster consists of a PG O-acetyltransferase A (patA) for translocation of acetate into the periplasm, a PG O-acetyltransferase B (patB) for O-acetylation, and an O-acetylpeptidoglycan esterase (ape1) for de-O-acetylation. In this study, reduced OAP in ΔpatA and ΔpatB had minimal impact on C. jejuni growth and fitness under the conditions tested. However, accumulation of OAP in Δape1 resulted in marked differences in PG biochemistry, including O-acetylation, anhydromuropeptide levels, and changes not expected to result directly from Ape1 activity. This suggests that OAP may be a form of substrate level regulation in PG biosynthesis. Ape1 acetylesterase activity was confirmed in vitro using p-nitrophenyl acetate and O-acetylated PG as substrates. In addition, Δape1 exhibited defects in pathogenesis-associated phenotypes, including cell shape, motility, biofilm formation, cell surface hydrophobicity, and sodium deoxycholate sensitivity. Δape1 was also impaired for chick colonization and adhesion, invasion, intracellular survival, and induction of IL-8 production in INT407 cells in vitro The importance of Ape1 in C. jejuni biology makes it a good candidate as an antimicrobial target.
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Affiliation(s)
- Reuben Ha
- From the Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Emilisa Frirdich
- From the Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - David Sychantha
- the Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - Jacob Biboy
- the Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne NE2 4AX, United Kingdom, and
| | - Michael E Taveirne
- the Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan 48109
| | - Jeremiah G Johnson
- the Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan 48109
| | - Victor J DiRita
- the Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan 48109
| | - Waldemar Vollmer
- the Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne NE2 4AX, United Kingdom, and
| | - Anthony J Clarke
- the Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - Erin C Gaynor
- From the Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada,
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Coronavirus receptor switch explained from the stereochemistry of protein-carbohydrate interactions and a single mutation. Proc Natl Acad Sci U S A 2016; 113:E3111-9. [PMID: 27185912 DOI: 10.1073/pnas.1519881113] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Hemagglutinin-esterases (HEs) are bimodular envelope proteins of orthomyxoviruses, toroviruses, and coronaviruses with a carbohydrate-binding "lectin" domain appended to a receptor-destroying sialate-O-acetylesterase ("esterase"). In concert, these domains facilitate dynamic virion attachment to cell-surface sialoglycans. Most HEs (type I) target 9-O-acetylated sialic acids (9-O-Ac-Sias), but one group of coronaviruses switched to using 4-O-Ac-Sias instead (type II). This specificity shift required quasisynchronous adaptations in the Sia-binding sites of both lectin and esterase domains. Previously, a partially disordered crystal structure of a type II HE revealed how the shift in lectin ligand specificity was achieved. How the switch in esterase substrate specificity was realized remained unresolved, however. Here, we present a complete structure of a type II HE with a receptor analog in the catalytic site and identify the mutations underlying the 9-O- to 4-O-Ac-Sia substrate switch. We show that (i) common principles pertaining to the stereochemistry of protein-carbohydrate interactions were at the core of the transition in lectin ligand and esterase substrate specificity; (ii) in consequence, the switch in O-Ac-Sia specificity could be readily accomplished via convergent intramolecular coevolution with only modest architectural changes in lectin and esterase domains; and (iii) a single, inconspicuous Ala-to-Ser substitution in the catalytic site was key to the emergence of the type II HEs. Our findings provide fundamental insights into how proteins "see" sugars and how this affects protein and virus evolution.
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Baumann AMT, Bakkers MJG, Buettner FFR, Hartmann M, Grove M, Langereis MA, de Groot RJ, Mühlenhoff M. 9-O-Acetylation of sialic acids is catalysed by CASD1 via a covalent acetyl-enzyme intermediate. Nat Commun 2015; 6:7673. [PMID: 26169044 PMCID: PMC4510713 DOI: 10.1038/ncomms8673] [Citation(s) in RCA: 82] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Accepted: 06/01/2015] [Indexed: 12/13/2022] Open
Abstract
Sialic acids, terminal sugars of glycoproteins and glycolipids, play important roles in development, cellular recognition processes and host–pathogen interactions. A common modification of sialic acids is 9-O-acetylation, which has been implicated in sialoglycan recognition, ganglioside biology, and the survival and drug resistance of acute lymphoblastic leukaemia cells. Despite many functional implications, the molecular basis of 9-O-acetylation has remained elusive thus far. Following cellular approaches, including selective gene knockout by CRISPR/Cas genome editing, we here show that CASD1—a previously identified human candidate gene—is essential for sialic acid 9-O-acetylation. In vitro assays with the purified N-terminal luminal domain of CASD1 demonstrate transfer of acetyl groups from acetyl-coenzyme A to CMP-activated sialic acid and formation of a covalent acetyl-enzyme intermediate. Our study provides direct evidence that CASD1 is a sialate O-acetyltransferase and serves as key enzyme in the biosynthesis of 9-O-acetylated sialoglycans. 9-O-Acetylation is one of the most common modifications of sialic acids, implicated in sialoglycan recognition and ganglioside biology. Here, the authors show that the key enzyme for the biosynthesis of 9-O-acetylated sialoglycans is CASD1, which uses CMP-activated sialic acid as acceptor substrate.![]()
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Affiliation(s)
- Anna-Maria T Baumann
- Institute of Cellular Chemistry, Hannover Medical School, D-30623 Hannover, Germany
| | - Mark J G Bakkers
- Virology Division, Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, 3584 CH Utrecht, The Netherlands
| | - Falk F R Buettner
- Institute of Cellular Chemistry, Hannover Medical School, D-30623 Hannover, Germany
| | - Maike Hartmann
- Institute of Cellular Chemistry, Hannover Medical School, D-30623 Hannover, Germany
| | - Melanie Grove
- Institute of Cellular Chemistry, Hannover Medical School, D-30623 Hannover, Germany
| | - Martijn A Langereis
- Virology Division, Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, 3584 CH Utrecht, The Netherlands
| | - Raoul J de Groot
- Virology Division, Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, 3584 CH Utrecht, The Netherlands
| | - Martina Mühlenhoff
- Institute of Cellular Chemistry, Hannover Medical School, D-30623 Hannover, Germany
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