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Abstract
Glycoscience assembles all the scientific disciplines involved in studying various molecules and macromolecules containing carbohydrates and complex glycans. Such an ensemble involves one of the most extensive sets of molecules in quantity and occurrence since they occur in all microorganisms and higher organisms. Once the compositions and sequences of these molecules are established, the determination of their three-dimensional structural and dynamical features is a step toward understanding the molecular basis underlying their properties and functions. The range of the relevant computational methods capable of addressing such issues is anchored by the specificity of stereoelectronic effects from quantum chemistry to mesoscale modeling throughout molecular dynamics and mechanics and coarse-grained and docking calculations. The Review leads the reader through the detailed presentations of the applications of computational modeling. The illustrations cover carbohydrate-carbohydrate interactions, glycolipids, and N- and O-linked glycans, emphasizing their role in SARS-CoV-2. The presentation continues with the structure of polysaccharides in solution and solid-state and lipopolysaccharides in membranes. The full range of protein-carbohydrate interactions is presented, as exemplified by carbohydrate-active enzymes, transporters, lectins, antibodies, and glycosaminoglycan binding proteins. A final section features a list of 150 tools and databases to help address the many issues of structural glycobioinformatics.
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Affiliation(s)
- Serge Perez
- Centre de Recherche sur les Macromolecules Vegetales, University of Grenoble-Alpes, Centre National de la Recherche Scientifique, Grenoble F-38041, France
| | - Olga Makshakova
- FRC Kazan Scientific Center of Russian Academy of Sciences, Kazan Institute of Biochemistry and Biophysics, Kazan 420111, Russia
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2
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Paul S, Samanta A. Ground- and Excited-State Interactions of a Psoralen Derivative with Human Telomeric G-Quadruplex DNA. J Phys Chem B 2018; 122:2277-2286. [PMID: 29376354 DOI: 10.1021/acs.jpcb.7b12475] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
G-quadruplex DNA has been a recent target for anticancer agents, and its binding interactions with small molecules, often used as anticancer drugs, have become an important area of research. Considering that psoralens have long been studied in the context of duplex DNA but that very little is known about their potential as G-quadruplex binders and their excited-state interaction with the latter has not been explored, we have studied herein the binding of a planar water-soluble psoralen derivative, 4'-aminomethyl-4,5',8-trimethylpsoralen (AMT), with the 22-mer human telomeric G-quadruplex-forming sequence, AGGG(TTAGGG)3, labeled here as (hTel22), and investigated the consequences of photoexcitation of AMT by calorimetric and spectroscopic techniques. The results show an enthalpy-driven 1:1 binding of AMT with hTel22 via end-stacking mode. Fluorescence quenching experiments on 6-fluorescein amidite-labeled oligomers indicate that the binding site is nearer to the 3' end of hTel22 in the diagonal loop region. Femtosecond time-resolved transient absorption measurements indicate electron transfer from the guanine moiety of hTel22 to photoexcited AMT, leading to the formation of a radical pair species (AMT•-G•+), which survives for 30 ps and is favored by a parallel/quasi-parallel orientation between the two. The findings reveal psoralens as a prospective class of compounds for the development of anticancer therapeutics by targeting the G-quadruplex DNA.
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Affiliation(s)
- Sneha Paul
- School of Chemistry, University of Hyderabad , Hyderabad 500046, India
| | - Anunay Samanta
- School of Chemistry, University of Hyderabad , Hyderabad 500046, India
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3
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Yang M, Simon R, MacKerell AD. Conformational Preference of Serogroup B Salmonella O Polysaccharide in Presence and Absence of the Monoclonal Antibody Se155-4. J Phys Chem B 2016; 121:3412-3423. [PMID: 28423910 DOI: 10.1021/acs.jpcb.6b08955] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Salmonella infection is a major public health problem worldwide. Antibodies directed toward the O polysaccharide (OPS) of S. Typhimurium, a serogroup B nontyphoidal Salmonella serovar, have protected against fatal infection in animal models. The OPS is known to undergo O-acetylation, though the impact of these modifications on antibody binding is poorly understood. Using molecular simulations, we assessed the conformational properties and antigen-antibody interactions of deacetylated and O-acetylated S. Typhimurium OPS when bound by monoclonal anti-OPS IgG Se155-4. Our findings indicate that (i) the α-d-abequose (8) monosaccharide makes important interactions with Se155-4, (ii) the deacetylated form binds to the antibody in two conformations, (iii) the acetyl group at α-l-rhamnose (5) traps the acetylated O-antigenic saccharide in one of those two conformations when bound to the antibody; (iv) the dominant conformation sampled by both unbound saccharides only occurs in the deacetylated-antibody complex; and (v) both unbound saccharides sample the second bound conformation to a small extent (2-4%). These observations provide insights into the conformational preference of an antigenic saccharide when bound to a well-characterized specific monoclonal antibody, and suggest possible important properties of vaccine induced antibodies following immunization with live attenuated and OPS-based subunit vaccines.
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Affiliation(s)
- Mingjun Yang
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland , Baltimore, Maryland 21201, United States
| | - Raphael Simon
- Center for Vaccine Development, Institute for Global Health, School of Medicine, University of Maryland , Baltimore, Maryland 21201, United States
| | - Alexander D MacKerell
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland , Baltimore, Maryland 21201, United States
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Multivalent display of minimal Clostridium difficile glycan epitopes mimics antigenic properties of larger glycans. Nat Commun 2016; 7:11224. [PMID: 27091615 PMCID: PMC4838876 DOI: 10.1038/ncomms11224] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Accepted: 02/26/2016] [Indexed: 12/31/2022] Open
Abstract
Synthetic cell-surface glycans are promising vaccine candidates against Clostridium difficile. The complexity of large, highly antigenic and immunogenic glycans is a synthetic challenge. Less complex antigens providing similar immune responses are desirable for vaccine development. Based on molecular-level glycan–antibody interaction analyses, we here demonstrate that the C. difficile surface polysaccharide-I (PS-I) can be resembled by multivalent display of minimal disaccharide epitopes on a synthetic scaffold that does not participate in binding. We show that antibody avidity as a measure of antigenicity increases by about five orders of magnitude when disaccharides are compared with constructs containing five disaccharides. The synthetic, pentavalent vaccine candidate containing a peptide T-cell epitope elicits weak but highly specific antibody responses to larger PS-I glycans in mice. This study highlights the potential of multivalently displaying small oligosaccharides to achieve antigenicity characteristic of larger glycans. The approach may result in more cost-efficient carbohydrate vaccines with reduced synthetic effort. Immunologically-active glycans are promising vaccine candidates but can be difficult to synthesize. Here, the authors show that pentavalent display of a minimal disaccharde epitope on a chemical scaffold can mimic a native C. difficile glycan antigen, representing a simple approach to synthetic vaccine production.
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Li M, Hoeck C, Schoffelen S, Gotfredsen CH, Meldal M. Specific Electrostatic Molecular Recognition in Water. Chemistry 2016; 22:7206-14. [PMID: 27073143 DOI: 10.1002/chem.201600231] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2016] [Indexed: 11/11/2022]
Abstract
The identification of pairs of small peptides that recognize each other in water exclusively through electrostatic interactions is reported. The target peptide and a structure-biased combinatorial ligand library consisting of ≈78 125 compounds were synthesized on different sized beads. Peptide-peptide interactions could conveniently be observed by clustering of the small, fluorescently labeled target beads on the surface of larger ligand-containing beads. Sequences of isolated hits were determined by MS/MS. The interactions of the complex showing the highest affinity were investigated by a novel single-bead binding assay and by 2D NMR spectroscopy. Molecular dynamics (MD) studies revealed a putative mode of interaction for this unusual electrostatic binding event. High binding specificity occurred through a combination of topological matching and electrostatic and hydrogen-bond complementarities. From MD simulations binding also seemed to involve three tightly bound water molecules in the interface between the binding partners. Binding constants in the submicromolar range, useful for biomolecular adhesion and in nanostructure design, were measured.
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Affiliation(s)
- Ming Li
- Department of Chemistry, Center for Evolutionary Chemical Biology, University of Copenhagen, Universitetsparken 5, 2100, Copenhagen, Denmark
| | - Casper Hoeck
- Department of Chemistry, Technical University of Denmark, Building 207, 2800, Kongens Lyngby, Denmark
| | - Sanne Schoffelen
- Department of Chemistry, Center for Evolutionary Chemical Biology, University of Copenhagen, Universitetsparken 5, 2100, Copenhagen, Denmark
| | - Charlotte H Gotfredsen
- Department of Chemistry, Technical University of Denmark, Building 207, 2800, Kongens Lyngby, Denmark
| | - Morten Meldal
- Department of Chemistry, Center for Evolutionary Chemical Biology, University of Copenhagen, Universitetsparken 5, 2100, Copenhagen, Denmark.
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6
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Haji-Ghassemi O, Blackler RJ, Martin Young N, Evans SV. Antibody recognition of carbohydrate epitopes†. Glycobiology 2015; 25:920-52. [PMID: 26033938 DOI: 10.1093/glycob/cwv037] [Citation(s) in RCA: 100] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2015] [Accepted: 05/24/2015] [Indexed: 12/14/2022] Open
Abstract
Carbohydrate antigens are valuable as components of vaccines for bacterial infectious agents and human immunodeficiency virus (HIV), and for generating immunotherapeutics against cancer. The crystal structures of anti-carbohydrate antibodies in complex with antigen reveal the key features of antigen recognition and provide information that can guide the design of vaccines, particularly synthetic ones. This review summarizes structural features of anti-carbohydrate antibodies to over 20 antigens, based on six categories of glyco-antigen: (i) the glycan shield of HIV glycoproteins; (ii) tumor epitopes; (iii) glycolipids and blood group A antigen; (iv) internal epitopes of bacterial lipopolysaccharides; (v) terminal epitopes on polysaccharides and oligosaccharides, including a group of antibodies to Kdo-containing Chlamydia epitopes; and (vi) linear homopolysaccharides.
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Affiliation(s)
- Omid Haji-Ghassemi
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC, Canada V8P 3P6
| | - Ryan J Blackler
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC, Canada V8P 3P6
| | - N Martin Young
- Human Health Therapeutics, National Research Council of Canada, 100 Sussex Drive, Ottawa, ON, Canada K1A 0R6
| | - Stephen V Evans
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC, Canada V8P 3P6
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Force fields and scoring functions for carbohydrate simulation. Carbohydr Res 2015; 401:73-81. [DOI: 10.1016/j.carres.2014.10.028] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2014] [Revised: 10/28/2014] [Accepted: 10/30/2014] [Indexed: 12/31/2022]
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8
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Lak P, Makeneni S, Woods RJ, Lowary TL. Specificity of furanoside-protein recognition through antibody engineering and molecular modeling. Chemistry 2014; 21:1138-48. [PMID: 25413161 DOI: 10.1002/chem.201405259] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2014] [Indexed: 01/06/2023]
Abstract
Recognition of furanosides (five-membered ring sugars) by proteins plays important roles in host-pathogen interactions. In comparison to their six-membered ring counterparts (pyranosides), detailed studies of the molecular motifs involved in the recognition of furanosides by proteins are scarce. Here the first in-depth molecular characterization of a furanoside-protein interaction system, between an antibody (CS-35) and cell wall polysaccharides of mycobacteria, including the organism responsible for tuberculosis is reported. The approach was centered on the generation of the single chain variable fragment of CS-35 and a rational library of its mutants. Investigating the interaction from various aspects revealed the structural motifs that govern the interaction, as well as the relative contribution of molecular forces involved in the recognition. The specificity of the recognition was shown to originate mainly from multiple CH-π interactions and, to a lesser degree, hydrogen bonds formed in critical distances and geometries.
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Affiliation(s)
- Parnian Lak
- Alberta Glycomics Centre and Department of Chemistry, University of Alberta, Edmonton, AB, T6G 2G2 (Canada)
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Marques F, Silva G, Thrash M, Dias-Cabral A. Lysozyme adsorption onto a cation-exchanger: Mechanism of interaction study based on the analysis of retention chromatographic data. Colloids Surf B Biointerfaces 2014; 122:801-807. [DOI: 10.1016/j.colsurfb.2014.08.024] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2014] [Revised: 08/16/2014] [Accepted: 08/18/2014] [Indexed: 10/24/2022]
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10
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Haji-Ghassemi O, Müller-Loennies S, Saldova R, Muniyappa M, Brade L, Rudd PM, Harvey DJ, Kosma P, Brade H, Evans SV. Groove-type recognition of chlamydiaceae-specific lipopolysaccharide antigen by a family of antibodies possessing an unusual variable heavy chain N-linked glycan. J Biol Chem 2014; 289:16644-61. [PMID: 24682362 DOI: 10.1074/jbc.m113.528224] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The structure of the antigen binding fragment of mAb S25-26, determined to 1.95 Å resolution in complex with the Chlamydiaceae family-specific trisaccharide antigen Kdo(2→8)Kdo(2→4)Kdo (Kdo = 3-deoxy-α-d-manno-oct-2-ulopyranosonic acid), displays a germ-line-coded paratope that differs significantly from previously characterized Chlamydiaceae-specific mAbs despite being raised against the identical immunogen. Unlike the terminal Kdo recognition pocket that promotes cross-reactivity in S25-2-type antibodies, S25-26 and the closely related S25-23 utilize a groove composed of germ-line residues to recognize the entire trisaccharide antigen and so confer strict specificity. Interest in S25-23 was sparked by its rare high μm affinity and strict specificity for the family-specific trisaccharide antigen; however, only the related antibody S25-26 proved amenable to crystallization. The structures of three unliganded forms of S25-26 have a labile complementary-determining region H3 adjacent to significant glycosylation of the variable heavy chain on asparagine 85 in Framework Region 3. Analysis of the glycan reveals a heterogeneous mixture with a common root structure that contains an unusually high number of terminal αGal-Gal moieties. One of the few reported structures of glycosylated mAbs containing these epitopes is the therapeutic antibody Cetuximab; however, unlike Cetuximab, one of the unliganded structures in S25-26 shows significant order in the glycan with appropriate electron density for nine residues. The elucidation of the three-dimensional structure of an αGal-containing N-linked glycan on a mAb variable heavy chain has potential clinical interest, as it has been implicated in allergic response in patients receiving therapeutic antibodies.
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Affiliation(s)
- Omid Haji-Ghassemi
- From the Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia V8P 3P6, Canada
| | - Sven Müller-Loennies
- Research Center Borstel, Leibniz-Center for Medicine and Biosciences, Parkallee 22, Borstel D-23845, Germany,
| | - Radka Saldova
- GlycoScience Group, the National Institute for Bioprocessing Research and Training (NIBRT), Mount Merrion, Blackrock, Dublin 4, Ireland
| | - Mohankumar Muniyappa
- GlycoScience Group, the National Institute for Bioprocessing Research and Training (NIBRT), Mount Merrion, Blackrock, Dublin 4, Ireland
| | - Lore Brade
- Research Center Borstel, Leibniz-Center for Medicine and Biosciences, Parkallee 22, Borstel D-23845, Germany
| | - Pauline M Rudd
- GlycoScience Group, the National Institute for Bioprocessing Research and Training (NIBRT), Mount Merrion, Blackrock, Dublin 4, Ireland
| | - David J Harvey
- Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom
| | - Paul Kosma
- University of Natural Resources and Life Sciences, Vienna, Austria, and
| | - Helmut Brade
- Research Center Borstel, Leibniz-Center for Medicine and Biosciences, Parkallee 22, Borstel D-23845, Germany
| | - Stephen V Evans
- From the Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia V8P 3P6, Canada,
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11
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Marchetti R, Canales A, Lanzetta R, Nilsson I, Vogel C, Reed DE, AuCoin DP, Jiménez-Barbero J, Molinaro A, Silipo A. Unraveling the Interaction between the LPS O-Antigen ofBurkholderia anthinaand the 5D8 Monoclonal Antibody by Using a Multidisciplinary Chemical Approach, with Synthesis, NMR, and Molecular Modeling Methods. Chembiochem 2013; 14:1485-93. [DOI: 10.1002/cbic.201300225] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2013] [Indexed: 11/11/2022]
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12
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Luo M, Velikovsky CA, Yang X, Siddiqui MA, Hong X, Barchi JJ, Gildersleeve JC, Pancer Z, Mariuzza RA. Recognition of the Thomsen-Friedenreich pancarcinoma carbohydrate antigen by a lamprey variable lymphocyte receptor. J Biol Chem 2013; 288:23597-606. [PMID: 23782692 DOI: 10.1074/jbc.m113.480467] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Variable lymphocyte receptors (VLRs) are leucine-rich repeat proteins that mediate adaptive immunity in jawless vertebrates. VLRs were recently shown to recognize glycans, such as the tumor-associated Thomsen-Friedenreich antigen (TFα; Galβ1-3GalNAcα), with a selectivity rivaling or exceeding that of lectins and antibodies. To understand the basis for TFα recognition by one such VLR (VLRB.aGPA.23), we measured thermodynamic parameters for the binding interaction and determined the structure of the VLRB.aGPA.23-TFα complex to 2.2 Å resolution. In the structure, four tryptophan residues form a tight hydrophobic cage encasing the TFα disaccharide that completely excludes buried water molecules. This cage together with hydrogen bonding of sugar hydroxyls to polar side chains explains the exquisite selectivity of VLRB.aGPA.23. The topology of the glycan-binding site of VLRB.aGPA.23 differs markedly from those of lectins or antibodies, which typically consist of long, convex grooves for accommodating the oligosaccharide. Instead, the TFα disaccharide is sandwiched between a variable loop and the concave surface of the VLR formed by the β-strands of the leucine-rich repeat modules. Longer oligosaccharides are predicted to extend perpendicularly across the β-strands, requiring them to bend to match the concavity of the VLR solenoid.
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Affiliation(s)
- Ming Luo
- University of Maryland Institute for Bioscience and Biotechnology Research, W. M. Keck Laboratory for Structural Biology, Rockville, Maryland 20850, USA
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Ghosh S, Kar A, Chowdhury S, Dasgupta D. Ellipticine binds to a human telomere sequence: an additional mode of action as a putative anticancer agent? Biochemistry 2013; 52:4127-37. [PMID: 23697684 DOI: 10.1021/bi400080t] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Polyguanine sequences fold into G-quadruplex structures in the presence of monovalent cations. It is accepted that the telomeric DNA region consists of G-quadruplex structure. There are reports that potential G-quadruplex forming motifs are also present in the promoter region of some proto-oncogenes such as c-myc, c-kit, KRAS, etc. Small molecules with the potential to stabilize the telomeric DNA quadruplex have emerged as potential anticancer agents. We have studied the interaction of ellipticine, a putative anticancer agent from a plant source, with a human telomeric DNA sequence (H24). Spectroscopic and calorimetric studies indicate that the association of ellipticine with H24 is an entropically driven phenomenon with a 2:3 (H24:ellipticine) stoichiometry. Though ellipticine binding does not induce any major structural perturbation in H24, the association leads to formation of a complex with enhanced thermal stability. An assay with the telomerase repeat amplification protocol shows that ellipticine inhibits telomerase activity in MDAMB-231 breast cancer cell line extracts. This is the first report of the quadruplex binding ability of ellipticine. Using the results, we propose that along with DNA intercalation and/or topoisomerase II inhibition, interaction with the telomeric DNA region and the resultant inhibition of telomerase activity might be an additional mode of action for its anticancer property.
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Affiliation(s)
- Saptaparni Ghosh
- Biophysics Division, Saha Institute of Nuclear Physics , Block-AF, Sector- I, Bidhan Nagar, Kolkata 700064, India
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Matsumoto-Takasaki A, Hanashima S, Aoki A, Yuasa N, Ogawa H, Sato R, Kawakami H, Mizuno M, Nakada H, Yamaguchi Y, Fujita-Yamaguchi Y. Surface plasmon resonance and NMR analyses of anti Tn-antigen MLS128 monoclonal antibody binding to two or three consecutive Tn-antigen clusters. J Biochem 2011; 151:273-82. [DOI: 10.1093/jb/mvr138] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
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15
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Oberli MA, Tamborrini M, Tsai YH, Werz DB, Horlacher T, Adibekian A, Gauss D, Möller HM, Pluschke G, Seeberger PH. Molecular analysis of carbohydrate-antibody interactions: case study using a Bacillus anthracis tetrasaccharide. J Am Chem Soc 2010; 132:10239-41. [PMID: 20614885 DOI: 10.1021/ja104027w] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The process for selecting potent and effective carbohydrate antigens is not well-established. A combination of synthetic glycan microarray screening, surface plasmon resonance analysis, and saturation transfer difference NMR spectroscopy was used to dissect the antibody-binding surface of a carbohydrate antigen, revealing crucial binding elements with atomic-level detail. This analysis takes the first step toward uncovering the rules for structure-based design of carbohydrate antigens.
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Affiliation(s)
- Matthias A Oberli
- Department of Biomolecular Systems, Max-Planck Institute for Colloids and Interfaces, 14476 Potsdam, Germany
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16
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Fadda E, Woods RJ. Molecular simulations of carbohydrates and protein-carbohydrate interactions: motivation, issues and prospects. Drug Discov Today 2010; 15:596-609. [PMID: 20594934 DOI: 10.1016/j.drudis.2010.06.001] [Citation(s) in RCA: 148] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2009] [Revised: 04/20/2010] [Accepted: 06/01/2010] [Indexed: 11/16/2022]
Abstract
The characterization of the 3D structure of oligosaccharides, their conjugates and analogs is particularly challenging for traditional experimental methods. Molecular simulation methods provide a basis for interpreting sparse experimental data and for independently predicting conformational and dynamic properties of glycans. Here, we summarize and analyze the issues associated with modeling carbohydrates, with a detailed discussion of four of the most recently developed carbohydrate force fields, reviewed in terms of applicability to natural glycans, carbohydrate-protein complexes and the emerging area of glycomimetic drugs. In addition, we discuss prospectives and new applications of carbohydrate modeling in drug discovery.
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Affiliation(s)
- Elisa Fadda
- School of Chemistry, National University of Ireland, Galway, Ireland
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17
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Sim L, Willemsma C, Mohan S, Naim HY, Pinto BM, Rose DR. Structural basis for substrate selectivity in human maltase-glucoamylase and sucrase-isomaltase N-terminal domains. J Biol Chem 2010; 285:17763-70. [PMID: 20356844 DOI: 10.1074/jbc.m109.078980] [Citation(s) in RCA: 156] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Human maltase-glucoamylase (MGAM) and sucrase-isomaltase (SI) are small intestinal enzymes that work concurrently to hydrolyze the mixture of linear alpha-1,4- and branched alpha-1,6-oligosaccharide substrates that typically make up terminal starch digestion products. MGAM and SI are each composed of duplicated catalytic domains, N- and C-terminal, which display overlapping substrate specificities. The N-terminal catalytic domain of human MGAM (ntMGAM) has a preference for short linear alpha-1,4-oligosaccharides, whereas N-terminal SI (ntSI) has a broader specificity for both alpha-1,4- and alpha-1,6-oligosaccharides. Here we present the crystal structure of the human ntSI, in apo form to 3.2 A and in complex with the inhibitor kotalanol to 2.15 A resolution. Structural comparison with the previously solved structure of ntMGAM reveals key active site differences in ntSI, including a narrow hydrophobic +1 subsite, which may account for its additional substrate specificity for alpha-1,6 substrates.
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Affiliation(s)
- Lyann Sim
- Department of Medical Biophysics, University of Toronto, Ontario Cancer Institute, Toronto, Ontario M56 2M9, Canada
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Roselin LS, Lin MS, Lin PH, Chang Y, Chen WY. Recent trends and some applications of isothermal titration calorimetry in biotechnology. Biotechnol J 2010; 5:85-98. [DOI: 10.1002/biot.200900092] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Moulik SP, Mitra D. Amphiphile self-aggregation: An attempt to reconcile the agreement–disagreement between the enthalpies of micellization determined by the van’t Hoff and Calorimetry methods. J Colloid Interface Sci 2009; 337:569-78. [DOI: 10.1016/j.jcis.2009.05.064] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2009] [Revised: 05/24/2009] [Accepted: 05/27/2009] [Indexed: 10/20/2022]
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20
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Sensitive and specific detection of the non-human sialic Acid N-glycolylneuraminic acid in human tissues and biotherapeutic products. PLoS One 2009; 4:e4241. [PMID: 19156207 PMCID: PMC2626223 DOI: 10.1371/journal.pone.0004241] [Citation(s) in RCA: 111] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2008] [Accepted: 12/09/2008] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Humans are genetically defective in synthesizing the common mammalian sialic acid N-glycolylneuraminic acid (Neu5Gc), but can metabolically incorporate it from dietary sources (particularly red meat and milk) into glycoproteins and glycolipids of human tumors, fetuses and some normal tissues. Metabolic incorporation of Neu5Gc from animal-derived cells and medium components also results in variable contamination of molecules and cells intended for human therapies. These Neu5Gc-incorporation phenomena are practically significant, because normal humans can have high levels of circulating anti-Neu5Gc antibodies. Thus, there is need for the sensitive and specific detection of Neu5Gc in human tissues and biotherapeutic products. Unlike monoclonal antibodies that recognize Neu5Gc only in the context of underlying structures, chicken immunoglobulin Y (IgY) polyclonal antibodies can recognize Neu5Gc in broader contexts. However, prior preparations of such antibodies (including our own) suffered from some non-specificity, as well as some cross-reactivity with the human sialic acid N-acetylneuraminic acid (Neu5Ac). METHODOLOGY/PRINCIPAL FINDINGS We have developed a novel affinity method utilizing sequential columns of immobilized human and chimpanzee serum sialoglycoproteins, followed by specific elution from the latter column by free Neu5Gc. The resulting mono-specific antibody shows no staining in tissues or cells from mice with a human-like defect in Neu5Gc production. It allows sensitive and specific detection of Neu5Gc in all underlying glycan structural contexts studied, and is applicable to immunohistochemical, enzyme-linked immunosorbent assay (ELISA), Western blot and flow cytometry analyses. Non-immune chicken IgY is used as a reliable negative control. We show that these approaches allow sensitive detection of Neu5Gc in human tissue samples and in some biotherapeutic products, and finally show an example of how Neu5Gc might be eliminated from such products, by using a human cell line grown under defined conditions. CONCLUSIONS We report a reliable antibody-based method for highly sensitive and specific detection of the non-human sialic acid Neu5Gc in human tissues and biotherapeutic products that has not been previously described.
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Grant CF, Kanda V, Yu H, Bundle DR, McDermott MT. Optimization of immobilized bacterial disaccharides for surface plasmon resonance imaging measurements of antibody binding. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:14125-32. [PMID: 19360960 DOI: 10.1021/la8026489] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The interactions between proteins and immobilized carbohydrates are crucial to biological events such as cell signaling and immune response. The modification of surfaces with carbohydrates to create sensing platforms provides a pathway to study these interactions in a laboratory setting. In this work, a family of structurally related Salmonella disaccharide epitopes is immobilized on thin gold films in an array format to probe antibody binding with surface plasmon resonance (SPR) imaging. The disaccharides are modified with an alkyl thiol linker for facile immobilization to gold. Small differences in the stereochemistry of the immobilized, modified disaccharides are shown to greatly influence the binding of a monoclonal antibody. Specifically, binding is only observed to an immobilized abequose dideoxyhexose relative to a tyvelose or a paratose analogue. However, both the amount and relative strength of bound antibody depends on the distribution of disaccharide moieties in a mixed monolayer of the epitope and a nonbinding diluent molecule. We thoroughly characterize the mixed monolayers with a variety of techniques to understand the optimal density and distribution of the disaccharide for antibody capture. This work reinforces the importance of controlling the density of ligands at the interface for optimized surface based bioassays.
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Affiliation(s)
- Chris F Grant
- Department of Chemistry and National Institute for Nanotechnology, University of Alberta, Edmonton, AB, Canada
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Thermodynamics and density of binding of a panel of antibodies to high-molecular-weight capsular polysaccharides. CLINICAL AND VACCINE IMMUNOLOGY : CVI 2008; 16:37-42. [PMID: 19005020 DOI: 10.1128/cvi.00290-08] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The interaction between antipolysaccharide (anti-PS) antibodies and their antigens was investigated by the use of isothermal titration calorimetry to determine the thermodynamic binding constant (K), the change in the enthalpy of binding (DeltaH), and the binding density (N) to high-molecular-weight PSs. From these values, the change in the entropy of binding (DeltaS) was calculated. The thermodynamic parameters of binding to high-molecular-weight capsular PSs are reported for two monoclonal antibodies (MAbs) with different specificities for meningococcal serogroup C PS, five MAbs specific for different pneumococcal serotypes, and the Fab fragments of two antipneumococcal MAbs. The K values were in the range of 10(6) to 10(7) M(-1), and these values were 1 to 2 orders of magnitude greater than the previously reported K values derived from antibody-oligosaccharide interactions. The DeltaH associated with binding was favorable for each MAb and Fab fragment. The DeltaS associated with binding was also generally favorable for both the MAbs and the Fab fragments, with the exception of the anti-serotype 14 MAb and its Fab fragment. N provides information regarding how densely MAbs or Fabs can bind along PS chains and, as expressed in terms of monosaccharides, was very similar for the seven MAbs, with an average of 12 monosaccharides per bound MAb. The value of N for each Fab was smaller, with five or seven monosaccharides per bound Fab. These results suggest that steric interactions between antibody molecules are a major influence on the values of N of high-affinity MAbs to capsular PSs.
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Dam TK, Torres M, Brewer CF, Casadevall A. Isothermal titration calorimetry reveals differential binding thermodynamics of variable region-identical antibodies differing in constant region for a univalent ligand. J Biol Chem 2008; 283:31366-70. [PMID: 18806257 DOI: 10.1074/jbc.m806473200] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The classical view of immunoglobulin molecules posits two functional domains defined by the variable (V) and constant (C) regions, which are responsible for antigen binding and antibody effector functions, respectively. These two domains are thought to function independently. However, several lines of evidence strongly suggest that C region domains can affect the specificity and affinity of an antibody for its antigen (Ag), independent of avidity-type effects. In this study, we used isothermal titration calorimetry to investigate the thermodynamic properties of the interactions of four V region-identical monoclonal antibodies with a univalent peptide antigen. Comparison of the binding of IgG1, IgG2a, IgG2b, and IgG3 with a 12-mer peptide mimetic of Cryptococcus neoformans polysaccharide revealed a stoichiometry of 1.9-2.0 with significant differences in thermodynamic binding parameters. Binding of this peptide to the antibodies was dominated by favorable entropy. The interaction of these antibodies with biotinylated peptides manifested greater enthalpy than for native peptides indicating that biotin labeling affected the types of Ag-Ab complexes formed. Our results provide unambiguous thermodynamic evidence for the notion that the C region can affect the interaction of the V region with an Ag.
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Affiliation(s)
- Tarun K Dam
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
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Padler-Karavani V, Yu H, Cao H, Chokhawala H, Karp F, Varki N, Chen X, Varki A. Diversity in specificity, abundance, and composition of anti-Neu5Gc antibodies in normal humans: potential implications for disease. Glycobiology 2008; 18:818-30. [PMID: 18669916 DOI: 10.1093/glycob/cwn072] [Citation(s) in RCA: 250] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Human heterophile antibodies that agglutinate animal erythrocytes are known to detect the nonhuman sialic acid N-glycolylneuraminic acid (Neu5Gc). This monosaccharide cannot by itself fill the binding site (paratope) of an antibody and can also be modified and presented in various linkages, on diverse underlying glycans. Thus, we hypothesized that the human anti-Neu5Gc antibody response is diverse and polyclonal. Here, we use a novel set of natural and chemoenzymatically synthesized glycans to show that normal humans have an abundant and diverse spectrum of such anti-Neu5Gc antibodies, directed against a variety of Neu5Gc-containing epitopes. High sensitivity and specificity assays were achieved by using N-acetylneuraminic acid (Neu5Ac)-containing probes (differing from Neu5Gc by one less oxygen atom) as optimal background controls. The commonest anti-Neu5Gc antibodies are of the IgG class. Moreover, the range of reactivity and Ig classes of antibodies vary greatly amongst normal humans, with some individuals having remarkably large amounts, even surpassing levels of some well-known natural blood group and xenoreactive antibodies. We purified these anti-Neu5Gc antibodies from individual human sera using a newly developed affinity method and showed that they bind to wild-type but not Neu5Gc-deficient mouse tissues. Moreover, they bind back to human carcinomas that have accumulated Neu5Gc in vivo. As dietary Neu5Gc is primarily found in red meat and milk products, we suggest that this ongoing antigen-antibody reaction may generate chronic inflammation, possibly contributing to the high frequency of diet-related carcinomas and other diseases in humans.
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Affiliation(s)
- Vered Padler-Karavani
- Glycobiology Research and Training Center and Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
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Ozen C, Norris AL, Land ML, Tjioe E, Serpersu EH. Detection of specific solvent rearrangement regions of an enzyme: NMR and ITC studies with aminoglycoside phosphotransferase(3')-IIIa. Biochemistry 2007; 47:40-9. [PMID: 18067326 DOI: 10.1021/bi701711j] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
This work describes differential effects of solvent in complexes of the aminoglycoside phosphotransferase(3')-IIIa (APH) with different aminoglycosides and the detection of change in solvent structure at specific sites away from substrates. Binding of kanamycins to APH occurs with a larger negative DeltaH in H2O relative to D2O (DeltaDeltaH(H2O-D2O) < 0), while the reverse is true for neomycins. Unusually large negative DeltaCp values were observed for binding of aminoglycosides to APH. DeltaCp for the APH-neomycin complex was -1.6 kcal x mol(-1) x deg(-1). A break at 30 degrees C was observed in the APH-kanamycin complex yielding DeltaCp values of -0.7 kcal x mol(-1) x deg(-1) and -3.8 kcal x mol(-1) x deg(-1) below and above 30 degrees C, respectively. Neither the change in accessible surface area (DeltaASA) nor contributions from heats of ionization were sufficient to explain the large negative DeltaCp values. Most significantly, 15N-1H HSQC experiments showed that temperature-dependent shifts of the backbone amide protons of Leu 88, Ser 91, Cys 98, and Leu143 revealed a break at 30 degrees C only in the APH-kanamycin complex in spectra collected between 21 degrees C and 38 degrees C. These amino acids represent solvent reorganization sites that experience a change in solvent structure in their immediate environment as structurally different ligands bind to the enzyme. These residues were away from the substrate binding site and distributed in three hydrophobic patches in APH. Overall, our results show that a large number of factors affect DeltaCp and binding of structurally different ligand groups cause different solvent structure in the active site as well as differentially affecting specific sites away from the ligand binding site.
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Affiliation(s)
- Can Ozen
- Graduate School of Genome Science and Technology, University of Tennessee and Oak Ridge National Laboratories, Knoxville, Tennessee 37996-0840, USA
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26
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Acierno JP, Braden BC, Klinke S, Goldbaum FA, Cauerhff A. Affinity Maturation Increases the Stability and Plasticity of the Fv Domain of Anti-protein Antibodies. J Mol Biol 2007; 374:130-46. [DOI: 10.1016/j.jmb.2007.09.005] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2007] [Revised: 08/13/2007] [Accepted: 09/05/2007] [Indexed: 11/26/2022]
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Cano J, Rodriguez A, Aicart E, Junquera E. Temperature effect on the complex formation between tricyclic antidepressant drugs (amitriptyline or imipramine) and hydroxypropyl-β-cyclodextrin in water. J INCL PHENOM MACRO 2007. [DOI: 10.1007/s10847-007-9328-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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28
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Kearney A, Avramovic A, Castro MAA, Carmo AM, Davis SJ, van der Merwe PA. The contribution of conformational adjustments and long-range electrostatic forces to the CD2/CD58 interaction. J Biol Chem 2007; 282:13160-6. [PMID: 17344209 PMCID: PMC2771598 DOI: 10.1074/jbc.m700829200] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
CD2 is a T cell surface molecule that enhances T and natural killer cell function by binding its ligands CD58 (humans) and CD48 (rodents) on antigen-presenting or target cells. Here we show that the CD2/CD58 interaction is enthalpically driven and accompanied by unfavorable entropic changes. Taken together with structural studies, this indicates that binding is accompanied by energetically significant conformational adjustments. Despite having a highly charged binding interface, neither the affinity nor the rate constants of the CD2/CD58 interaction were affected by changes in ionic strength, indicating that long-range electrostatic forces make no net contribution to binding.
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Affiliation(s)
- Alice Kearney
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, United Kingdom
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Gupta S, Das L, Datta AB, Poddar A, Janik ME, Bhattacharyya B. Oxalone and Lactone Moieties of Podophyllotoxin Exhibit Properties of Both the B and C Rings of Colchicine in Its Binding with Tubulin. Biochemistry 2006; 45:6467-75. [PMID: 16700557 DOI: 10.1021/bi060178j] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Thermodynamics of podophyllotoxin binding to tubulin and its multiple points of attachment with tubulin has been studied in detail using isothermal titration calorimetry. The calorimetric enthalpy of the association of podophyllotoxin with tubulin is negative and occurs with a negative heat capacity change (DeltaC(p) = -2.47 kJ mol(-)(1) K(-)(1)). The binding is unique with a simultaneous participation of both hydrophobic and hydrogen-bonding forces with unfavorable negative entropic contribution at higher temperature, favored with an enthalpy-entropy compensation. Interestingly, the binding of 2-methoxy-5-(2',3',4'-trimethoxyphenyl)tropone (AC, a colchicine analogue without the B ring) with tubulin is enthalpy-favored. However, the podophyllotoxin-tubulin association depending upon the temperature of the reaction has a favorable entropic and enthalpic component, which resembles both B- and C-ring properties of colchicine. On the basis of the crystal structure of the podophyllotoxin-tubulin complex, distance calculations have indicated a possible interaction between threonine 179 of alpha-tubulin and the hydroxy group on the D ring of podophyllotoxin. To confirm the involvement of the oxalone moiety as well as the lactone ring of podophyllotoxin in tubulin binding, analogues of podophyllotoxin are synthesized with methoxy substitution at the 4' position of ring D along with its isomer and another analogue epimerized at ring E. From these results, involvement of oxalone as well as the lactone ring of the drug in a specific orientation inclusive of ring A is indicated for podophyllotoxin-tubulin binding. Therefore, podophyllotoxin, like colchicine, behaves as a bifunctional ligand having properties of both the B and C rings of colchicine by making more than one point of attachment with the protein tubulin.
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Affiliation(s)
- Suvroma Gupta
- Department of Biochemistry, Bose Institute, Centenary Campus, P-1/12, CIT Scheme VII M, Calcutta 700054, India
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Gilbert SD, Stoddard CD, Wise SJ, Batey RT. Thermodynamic and kinetic characterization of ligand binding to the purine riboswitch aptamer domain. J Mol Biol 2006; 359:754-68. [PMID: 16650860 DOI: 10.1016/j.jmb.2006.04.003] [Citation(s) in RCA: 227] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2006] [Revised: 03/31/2006] [Accepted: 04/01/2006] [Indexed: 01/06/2023]
Abstract
Riboswitches are cis-acting genetic regulatory elements found commonly in bacterial mRNAs that consist of a metabolite-responsive aptamer domain coupled to a regulatory switch. Purine riboswitches respond to intracellular concentrations of either adenine or guanine/hypoxanthine to control gene expression. The aptamer domain of the purine riboswitch contains a pyrimidine residue (Y74) that forms a Watson-Crick base-pairing interaction with the bound purine nucleobase ligand that discriminates between adenine and guanine. We sought to understand the structural basis of this specificity and the mechanism of ligand recognition by the purine riboswitch. Here, we present the 2,6-diaminopurine-bound structure of a C74U mutant of the xpt-pbuX guanine riboswitch, along with a detailed thermodynamic and kinetic analysis of nucleobase recognition by both the native and mutant riboswitches. These studies demonstrate clearly that the pyrimidine at position 74 is the sole determinant of purine riboswitch specificity. In addition, the mutant riboswitch binds adenine and adenine derivatives well compared with the guanine-responsive riboswitch. Under our experimental conditions, 2,6-diaminopurine binds the RNA with DeltaH=-40.3 kcal mol(-1), DeltaS=-97.6 cal mol(-1)K(-1), and DeltaG=-10.73 kcal mol(-1). A kinetic determination of the slow rate (0.15 x 10(5)M(-1)s(-1) and 2.1 x 10(5)mM(-1)s(-1) for 2-aminopurine binding the adenine-responsive mutant riboswitch and 7-deazaguanine-binding guanine riboswitch, respectively) of association under varying experimental conditions allowed us to propose a mechanism for ligand recognition by the purine riboswitch. A conformationally dynamic unliganded state for the binding pocket is stabilized first by the Watson-Crick base pairing between the ligand and Y74, and by the subsequent ordering of the J2/3 loop, enclosing the ligand within the three-way junction.
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Affiliation(s)
- Sunny D Gilbert
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, Boulder, CO 80309, USA
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Abstract
We have a limited understanding of the details of molecular recognition of carbohydrates by proteins, which is critical to a multitude of biological processes. Furthermore, carbohydrate-modifying proteins such as glycosyl hydrolases and phosphorylases are of growing importance as potential drug targets. Interactions between proteins and carbohydrates have complex thermodynamics, and in general the specific positioning of only a few hydroxyl groups determines their binding affinities. A thorough understanding of both carbohydrate and protein structures is thus essential to predict these interactions. An atomic-level view of carbohydrate recognition through structures of carbohydrate-active enzymes complexed with transition-state inhibitors reveals some of the distinctive molecular features unique to protein-carbohydrate complexes. However, the inherent flexibility of carbohydrates and their often water-mediated hydrogen bonding to proteins makes simulation of their complexes difficult. Nonetheless, recent developments such as the parameterization of specific force fields and docking scoring functions have greatly improved our ability to predict protein-carbohydrate interactions. We review protein-carbohydrate complexes having defined molecular requirements for specific carbohydrate recognition by proteins, providing an overview of the different computational techniques available to model them.
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Affiliation(s)
- Alain Laederach
- Department of Chemical Engineering, Iowa State University, Ames, Iowa 50011-2230, USA
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Abstract
Thermodynamics governs the process of biomolecular recognition. The steps of characterizing, understanding and exploiting binding thermodynamics have the potential to contribute to an improved rational drug design process that is more robust and reliable. It is only relatively recently that instrumentation capable of direct and full thermodynamic characterization has been improved, giving impetus to the application of thermodynamic measurements in drug discovery. This review highlights current instruments and methods that can be employed to measure binding thermodynamics and their use in studies of biomolecular recognition and drug discovery.
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Affiliation(s)
- Geoffrey A Holdgate
- Molecular Enzymology Group, AstraZeneca, Alderley Park, Macclesfield, Cheshire SK10 4TG, UK.
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Boraston A. The interaction of carbohydrate-binding modules with insoluble non-crystalline cellulose is enthalpically driven. Biochem J 2005; 385:479-84. [PMID: 15487986 PMCID: PMC1134719 DOI: 10.1042/bj20041473] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Natural cellulose exists as a composite of cellulose forms, which can be broadly characterized as crystalline or non-crystalline. The recognition of both of these forms of cellulose by the CBMs (carbohydrate-binding modules) of microbial glycoside hydrolases is important for the efficient natural and biotechnological conversion of cellulosic biomass. The category of CBM that binds insoluble non-crystalline cellulose does so with an affinity approx. 10-20-fold greater than their affinity for cello-oligosaccharides and/or soluble polysaccharides. This phenomenon has been assumed to originate from the effects of changes in configurational entropy upon binding. The loss of configurational entropy is thought to be less profound upon binding to conformationally restrained insoluble non-crystalline cellulose, resulting in larger free energies of binding. However, using isothermal titration calorimetry, it is shown that this is not the case for the high-affinity interactions of CcCBM17 (the family 17 CBM from EngF of Clostridium cellulovorans) and BspCBM28 (the family 28 CBM from Cel5A of Bacillus species 1139) with regenerated cellulose, an insoluble preparation of primarily non-crystalline cellulose. The enhanced free energy of binding of non-crystalline cellulose relative to cello-oligosaccharides is by virtue of improved enthalpy, not entropy.
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Affiliation(s)
- Alisdair B. Boraston
- Biochemistry & Microbiology, University of Victoria, P.O. Box 3055 STN CSC, Victoria, British Columbia, Canada V8W 3P6
- email
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Sultan NAM, Swamy MJ. Energetics of carbohydrate binding to Momordica charantia (bitter gourd) lectin: an isothermal titration calorimetric study. Arch Biochem Biophys 2005; 437:115-25. [PMID: 15820223 DOI: 10.1016/j.abb.2005.03.005] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2005] [Revised: 03/04/2005] [Indexed: 10/25/2022]
Abstract
Physico-chemical and carbohydrate binding studies have been carried out on the Momordica charantia (bitter gourd) seed lectin (MCL). The lectin activity is maximal in the pH range 7.4-11.0, but decreases steeply below pH 7.0. The lectin activity is mostly unaffected in the temperature range 4-50 degrees C, but a sharp decrease is seen between 50 and 60 degrees C, which could be correlated to changes in the structure of the protein as seen by circular dichroism and fluorescence spectroscopy. Isothermal titration calorimetric studies show that the tetrameric MCL binds two sugar molecules and the binding constants (Kb), determined at 288.15 K, for various saccharides were found to vary between 7.3 x 10(3) and 1.52 x 10(4)M(-1). The binding reactions for all the saccharides investigated were essentially enthalpy driven, with the binding enthalpies (DeltaHb) at 288.15 K being in the range of -50.99 and -43.39 kJ mol(-1), whereas the contribution to the binding reaction from the entropy of binding was negative, with values of binding entropy (DeltaSb) ranging between -99.2 and -72.0 J mol(-1)K(-1) at 288.15 K. Changes in heat capacity (DeltaCp) for the binding of disaccharides, lactose and lactulose, were significantly larger in magnitude than those obtained for the monosaccharides, methyl-beta-D-galactopyranoside, and methyl-alpha-D-galactopyranoside, and could be correlated reasonably well with the surface areas of these ligands. Enthalpy-entropy compensation was observed for all the sugars studied, suggesting that water structure plays an important role in the overall binding reaction. CD spectroscopy indicates that carbohydrate binding does not lead to significant changes in the secondary and tertiary structures of MCL, suggesting that the carbohydrate binding sites on this lectin are mostly preformed.
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Daranas AH, Shimizu H, Homans SW. Thermodynamics of binding of D-galactose and deoxy derivatives thereof to the L-arabinose-binding protein. J Am Chem Soc 2005; 126:11870-6. [PMID: 15382922 DOI: 10.1021/ja048054m] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We report the thermodynamics of binding of d-galactose and deoxy derivatives thereof to the arabinose binding protein (ABP). The "intrinsic" (solute-solute) free energy of binding DeltaG degrees (int) at 308 K for the 1-, 2-, 3-, and 6-hydroxyl groups of galactose is remarkably constant (approximately -30 kJ/mol), despite the fact that each hydroxyl group subtends different numbers of hydrogen bonds in the complex. The substantially unfavorable enthalpy of binding (approximately 30 kJ/mol) of 1-deoxygalactose, 2-deoxygalactose, and 3-deoxygalactose in comparison with galactose, cannot be readily accounted for by differences in solvation, suggesting that solute-solute hydrogen bonds are enthalpically significantly more favorable than solute-solvent hydrogen bonds. In contrast, the substantially higher affinity for 2-deoxygalactose in comparison with either 1-deoxygalactose or 3-deoxygalactose derives from differences in the solvation free energies of the free ligands.
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Affiliation(s)
- Antonio Hernandez Daranas
- Astbury Centre for Structural Molecular Biology, School of Biochemistry and Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
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Haroun M, Ravelet C, Ravel A, Grosset C, Villet A, Peyrin E. Thermodynamic origin of the chiral recognition of tryptophan on teicoplanin and teicoplanin aglycone stationary phases. J Sep Sci 2005; 28:409-20. [PMID: 15835728 DOI: 10.1002/jssc.200400043] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The D-, L-tryptophan binding and the chiral recognition properties of the teicoplanin and teicoplanin aglycone (TAG) chiral stationary phase (CSPs) were compared at various column temperatures. The solute adsorption isotherms (bi-Langmuir model) were determined for both the two CSPs using the perturbation method. It was demonstrated that the sugar units were involved in the reduction of the apparent enantioselectivity through two phenomena: (i) the inhibition of some enantioselective contacts with low-affinity binding regions of the aglycone and (ii) a decrease in the stereoselective properties of the aglycone high-affinity binding pocket. The phenomenon (ii) was governed by both a decrease in the ratio of the enantiomer adsorption constant and a strong reduction of the site accessibility for D- and L-tryptophan. In addition, a temperature effect study was performed to investigate the chiral recognition mechanism at the aglycone high-affinity pocket. An enthalpy-entropy compensation analysis derived from the Grunwald model as well as the comparison with the literature data demonstrated that the enantioselective binding mode was dependent on an interface dehydration process. The change in the enantioselective process observed between the TAG and teicoplanin CSP was characterized by a difference of ca. 2-3 ordered water molecules released from the species interface.
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Affiliation(s)
- Mohamed Haroun
- Département de Pharmacochimie Moléculaire, UMR 5063 CNRS, ICMG FR 2607, UFR de Pharmacie, Université Joseph Fourier, Grenoble, France
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Lo MC, Aulabaugh A, Jin G, Cowling R, Bard J, Malamas M, Ellestad G. Evaluation of fluorescence-based thermal shift assays for hit identification in drug discovery. Anal Biochem 2005; 332:153-9. [PMID: 15301960 DOI: 10.1016/j.ab.2004.04.031] [Citation(s) in RCA: 506] [Impact Index Per Article: 26.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2004] [Indexed: 11/22/2022]
Abstract
The fluorescence-based thermal shift assay is a general method for identification of inhibitors of target proteins from compound libraries. Using an environmentally sensitive fluorescent dye to monitor protein thermal unfolding, the ligand-binding affinity can be assessed from the shift of the unfolding temperature (Delta Tm) obtained in the presence of ligands relative to that obtained in the absence of ligands. In this article, we report that the thermal shift assay can be conducted in an inexpensive, commercially available device for temperature control and fluorescence detection. The binding affinities obtained from thermal shift assays are compared with the binding affinities measured by isothermal titration calorimetry and with the IC(50) values from enzymatic assays. The potential pitfalls in the data analysis of thermal shift assays are also discussed.
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Affiliation(s)
- Mei-Chu Lo
- Biophysics/Enzymology-Chemical and Screening Sciences, Wyeth Research, Pearl River, NY 10965, USA.
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39
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Affiliation(s)
- Trine Christensen
- Department of Chemistry, Duke University, Durham, North Carolina 27708, USA
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40
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Zechel DL, Boraston AB, Gloster T, Boraston CM, Macdonald JM, Tilbrook DMG, Stick RV, Davies GJ. Iminosugar Glycosidase Inhibitors: Structural and Thermodynamic Dissection of the Binding of Isofagomine and 1-Deoxynojirimycin to β-Glucosidases. J Am Chem Soc 2003; 125:14313-23. [PMID: 14624580 DOI: 10.1021/ja036833h] [Citation(s) in RCA: 134] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The design and synthesis of transition-state mimics reflects the growing need both to understand enzymatic catalysis and to influence strategies for therapeutic intervention. Iminosugars are among the most potent inhibitors of glycosidases. Here, the binding of 1-deoxynojirimycin and (+)-isofagomine to the "family GH-1" beta-glucosidase of Thermotoga maritima is investigated by kinetic analysis, isothermal titration calorimetry, and X-ray crystallography. The binding of both of these iminosugar inhibitors is driven by a large and favorable enthalpy. The greater inhibitory power of isofagomine, relative to 1-deoxynojirimycin, however, resides in its significantly more favorable entropy; indeed the differing thermodynamic signatures of these inhibitors are further highlighted by the markedly different heat capacity values for binding. The pH dependence of catalysis and of inhibition suggests that the inhibitory species are protonated inhibitors bound to enzymes whose acid/base and nucleophile are ionized, while calorimetry indicates that one proton is released from the enzyme upon binding at the pH optimum of catalysis (pH 5.8). Given that these results contradict earlier proposals that the binding of racemic isofagomine to sweet almond beta-glucosidase was entropically driven (Bülow, A. et al. J. Am. Chem. Soc. 2000, 122, 8567-8568), we reinvestigated the binding of 1-deoxynojirimycin and isofagomine to the sweet almond enzyme. Calorimetry confirms that the binding of isofagomine to sweet almond beta-glucosidases is, as observed for the T. maritima enzyme, driven by a large favorable enthalpy. The crystallographic structures of the native T. maritima beta-glucosidase, and its complexes with isofagomine and 1-deoxynojirimycin, all at approximately 2.1 A resolution, reveal that additional ordering of bound solvent may present an entropic penalty to 1-deoxynojirimycin binding that does not penalize isofagomine.
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Affiliation(s)
- David L Zechel
- Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York YO10 5YW, United Kingdom
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41
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Williams CK, Galley WC, Brown GR. The influence of competing factors on the endothermic nature of bile salt binding by cationic adsorbent. CAN J CHEM 2003. [DOI: 10.1139/v03-003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The binding of sodium chenodeoxycholate, a hydrophobic bile salt, by a polyacrylamide resin with N,N,N-trimethylammonium dodecyl chloride (QPDA12) pendant groups was studied in the presence of elevated concentrations of competing anions. The equilibrium bile salt concentration was determined from HPLC data for a range of initial bile salt concentrations. Binding constants extracted from the fit of the isotherms to the Langmuir equation were obtained for data for temperatures from 24 to 60°C. A reduction in chenodeoxycholate binding affinity was observed in comparison with that reported previously at lower overall anion concentrations. A van't Hoff analysis of the data revealed that a decrease in the favourable entropy of binding was responsible for this reduced affinity. Decomposition of the binding constants into specific contributions for the competing buffer anions and the chenodeoxycholate anion returned positive values of ΔH° and ΔS° for the binding of both the competing ions and bile salt. These findings reveal that the weakening of the bile salt binding that occurs with added salt is not due to Debye screening of an attraction between ions of opposite charge. A binding mechanism consistent with the thermodynamics observed was proposed in which the dominant role of hydration changes that occur on binding provides the principal driving force for the process.Key words: bile salts, endothermic binding, polymer sorbents, solvent randomization.
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42
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Yu HN, Ling CC, Bundle DR. Synthesis of threeSalmonellaepitopes for biosensor studies of carbohydrateantibody interactions. CAN J CHEM 2002. [DOI: 10.1139/v02-121] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Disaccharides 1-3 corresponding to the antigenic determinants of Salmonella serotypes A, B, and D1were synthesized in a form suited for use in biosensors. The disaccharide determinants each contain a unique 3,6-dideoxyhexose, namely abequose (3,6-dideoxy-D-xylo-hexose), paratose (3,6-dideoxy-D-ribohexose), and tyvelose (3,6-dideoxy-D-arabino-hexose), are α-linked to the 3-position of D-mannopyranose. The disaccharides were further derivatized with a linear aglycon that has a terminal amino group, and can be readily coupled to pertinent chains carrying a terminal thiol for the construction of self-assembled monolayers (SAMs). Efficient routes that employed a single 3,6-dideoxygenation step were developed for the synthesis of paratoside 15 and tyveloside 22.Key words: Salmonella O-antigens, lipopolysaccharide, abequose, paratose, tyvelose, 3,6-dideoxyhexose, deoxygenation, glycoside tethers, immobilization via pentenyl glycosides.
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43
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Lowary TL, Eichler E, Bundle DR. Oligosaccharide recognition by antibodies: Synthesis and evaluation of talose oligosaccharide analogues. CAN J CHEM 2002. [DOI: 10.1139/v02-118] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A series of monosaccharide (46), disaccharide (3,712), and trisaccharide (1315) analogs of the native ligand 2, which fills the binding site of monoclonal antibody Se 155.4, have been synthesized and their bioactivity measured by solid- and solution-phase assays. The syntheses of disaccharide analogs sought to replace galactose by various alkyl groups at the O-2 position of mannose. The activity of one of these O-2 alkyl analogs was 75% of that observed for the trisaccharide and points to only weak net bonding between the solvent exposed galactose residue and the antibody binding site. The synthesis of talose analogs 13 and 14, where the mannose or galactose residues of 2 were replaced by talose produced ligands with activities from one-third to one-half of that seen for the native ligand 2. These activity changes did not exhibit discernable correlations with the ability of talose to disrupt water of solvation.Key words: abequose, 3,6-dideoxy-D-xylo-hexose, talose disaccharide and trisaccharide, antibody oligosaccharide interactions, molecular recognition of carbohydrates, water in antibody complexes, Salmonella LPS, monoclonal antibody Se 155.4, bacterial O-antigen.
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44
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Uhrín D, Prasad AK, Brisson JR, Bundle DR. Carbohydrate-antibody interactions by NMR for a13C-labelled disaccharide ligand. CAN J CHEM 2002. [DOI: 10.1139/v02-063] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Incorporation of a13C label into a carbohydrate ligand, methyl 3-O-(3,6-dideoxy-α-D-xylohexopyranosyl)-2-O-methyl-α-D-mannopyranoside permitted by NMR spectroscopy the study of its binding to the Fab from a monoclonal antibody, Se 155-4. The signals of the free and bound form were observed in the13C spectrum of the carbohydrate-protein complex. The dissociation rate constants were consequently determined by full lineshape analysis of the13C spectrum. Comparison with simplified analyses relying only on the linewidth of the1H and13C signals of the free ligand were made and the justifications of underlying assumptions used in these analyses were discussed. For1H NMR, the protein resonances were purged with a13C filter to observe only the ligand resonances and NOEs between the ligand and the protein.Key words: carbohydrate, binding, NMR, C-13 label, chemical exchange.
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45
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Boraston AB, Nurizzo D, Notenboom V, Ducros V, Rose DR, Kilburn DG, Davies GJ. Differential oligosaccharide recognition by evolutionarily-related beta-1,4 and beta-1,3 glucan-binding modules. J Mol Biol 2002; 319:1143-56. [PMID: 12079353 DOI: 10.1016/s0022-2836(02)00374-1] [Citation(s) in RCA: 126] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Enzymes active on complex carbohydrate polymers frequently have modular structures in which a catalytic domain is appended to one or more carbohydrate-binding modules (CBMs). Although CBMs have been classified into a number of families based upon sequence, many closely related CBMs are specific for different polysaccharides. In order to provide a structural rationale for the recognition of different polysaccharides by CBMs displaying a conserved fold, we have studied the thermodynamics of binding and three-dimensional structures of the related family 4 CBMs from Cellulomonas fimi Cel9B and Thermotoga maritima Lam16A in complex with their ligands, beta-1,4 and beta-1,3 linked gluco-oligosaccharides, respectively. These two CBMs use a structurally conserved constellation of aromatic and polar amino acid side-chains that interact with sugars in two of the five binding subsites. Differences in the length and conformation of loops in non-conserved regions create binding-site topographies that complement the known solution conformations of their respective ligands. Thermodynamics interpreted in the light of structural information highlights the differential role of water in the interaction of these CBMs with their respective oligosaccharide ligands.
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Affiliation(s)
- Alisdair B Boraston
- Protein Engineering Network of Centres of Excellence, Edmonton, Alberta, Canada T6G 2S2
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46
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Hegde SS, Dam TK, Brewer CF, Blanchard JS. Thermodynamics of aminoglycoside and acyl-coenzyme A binding to the Salmonella enterica AAC(6')-Iy aminoglycoside N-acetyltransferase. Biochemistry 2002; 41:7519-27. [PMID: 12044186 DOI: 10.1021/bi020190l] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Kinetic and mechanistic studies on the chromosomally encoded aminoglycoside 6'-N-acetyltransferase, AAC(6')-Iy, of Salmonella enterica that confers resistance toward aminoglycosides have been previously reported [Magnet et al. (2001) Biochemistry 40, 3700-3709]. In the present study, equilibrium binding and the thermodynamic parameters of binding of aminoglycosides and acyl-coenzyme A derivatives to AAC(6')-Iy and of two mutants, C109A and the C109A/C70A double mutant, have been studied using fluorescence spectroscopy and isothermal titration calorimetry (ITC). Association constants for different aminoglycosides varied greatly (4 x 10(4)-150 x 10(4)) while the association constants of several acyl-coenzyme A derivatives were similar (3.2 x 10(4)-4.5 x 10(4)). The association constants and van't Hoff enthalpy changes derived from intrinsic protein fluorescence changes were in agreement with independently measured values from isothermal titration calorimetry studies. Binding of both aminoglycosides and acyl-coenzyme A derivatives is strongly enthalpically driven and revealed opposing negative entropy changes, resulting in enthalpy-entropy compensation. The acetyltransferase exhibited a temperature-dependent binding of tobramycin with a negative heat capacity value of 410 cal mol(-1) K(-1). Isothermal titration studies of acetyl-coenzyme A and tobramycin binding to mutant forms of the enzyme indicated that completely conserved C109 does not play any direct role in the binding of either of the substrates, while C70 is directly involved in aminoglycoside binding. These results are discussed and compared with previous steady-state kinetic studies of the enzyme.
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Affiliation(s)
- Subray S Hegde
- Departments of Biochemistry and Molecular Pharmacology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA
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47
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Horn JR, Brandts JF, Murphy KP. van't Hoff and calorimetric enthalpies II: effects of linked equilibria. Biochemistry 2002; 41:7501-7. [PMID: 12044184 DOI: 10.1021/bi025626b] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The complexity of binding reactions, including the linkage with other equilibria, is becoming increasingly apparent in biological processes such as signal transduction. Understanding these interactions requires obtaining thermodynamic profiles for each of the equilibria that occur in a binding event. Concern has been raised as to whether linked equilibria contribute differently to thermodynamics, such as DeltaH degrees and DeltaC(p), obtained from calorimetric and van't Hoff methods. We have previously shown that linked equilibria do not contribute differently to the van't Hoff and calorimetrically determined DeltaH degrees for processes such as linked folding or hydration. Here, examples of proton and ion linkage are examined. We show that there is no reason to expect the calorimetric and van't Hoff DeltaH degrees to be different, even without prior knowledge of the presence or absence of linked equilibria, as long as the system is permitted to equilibrate. However, it is possible to create experimental scenarios that result in and discrepancies. Furthermore, it is found that the presence of linked equilibria in all cases can result in "nonconventional" DeltaH degrees and DeltaC(p) profiles, making data analysis nontrivial.
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Affiliation(s)
- James R Horn
- Department of Biochemistry, College of Medicine, University of Iowa, Iowa City, IA 52242, USA
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48
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Wu P, Nakano SI, Sugimoto N. Temperature dependence of thermodynamic properties for DNA/DNA and RNA/DNA duplex formation. EUROPEAN JOURNAL OF BIOCHEMISTRY 2002; 269:2821-30. [PMID: 12071944 DOI: 10.1046/j.1432-1033.2002.02970.x] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
A clear difference in the enthalpy changes derived from spectroscopic and calorimetric measurements has recently been shown. The exact interpretation of this deviation varied from study to study, but it was generally attributed to the non-two-state transition and heat capacity change. Although the temperature-dependent thermodynamics of the duplex formation was often implied, systemic and extensive studies have been lacking in universally assigning the appropriate thermodynamic parameter sets. In the present study, the 24 DNA/DNA and 41 RNA/DNA oligonucleotide duplexes, designed to avoid the formation of hairpin or slipped duplex structures and to limit the base pair length less than 12 bp, were selected to evaluate the heat capacity changes and temperature-dependent thermodynamic properties of duplex formation. Direct comparison reveals that the temperature-independent thermodynamic parameters could provide a reasonable approximation only when the temperature of interest has a small deviation from the mean melting temperature over the experimental range. The heat capacity changes depend on the base composition and sequences and are generally limited in the range of -160 to approximately -40 cal.mol-1.K-1 per base pair. In contrast to the enthalpy and entropy changes, the free energy change and melting temperature are relatively insensitive to the heat capacity change. Finally, the 16 NN-model free energy parameters and one helix initiation at physiological temperature were extracted from the temperature-dependent thermodynamic data of the 41 RNA/DNA hybrids.
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Affiliation(s)
- Peng Wu
- High Technology Research Center, Faculty of Science and Engineering, Konan University, Okamoto, Higashinada-ku, Japan
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49
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Ward WH, Holdgate GA. Isothermal titration calorimetry in drug discovery. PROGRESS IN MEDICINAL CHEMISTRY 2002; 38:309-76. [PMID: 11774798 DOI: 10.1016/s0079-6468(08)70097-3] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
Isothermal titration calorimetry (ITC) follows the heat change when a test compound binds to a target protein. It allows precise measurement of affinity. The method is direct, making interpretation facile, because there is no requirement for competing molecules. Titration in the presence of other ligands rapidly provides information on the mechanism of action of the test compound, identifying the intermolecular complexes that are relevant for structure-based design. Calorimetry allows measurement of stoichiometry and so evaluation of the proportion of the sample that is functional. ITC can characterize protein fragments and catalytically inactive mutant enzymes. It is the only technique which directly measures the enthalpy of binding (delta H degree). Interpretation of delta H degree and its temperature dependence (delta Cp) is usually qualitative, not quantitative. This is because of complicated contributions from linked equilibria and a single change in structure giving modification of several physicochemical properties. Measured delta H degree values allow characterization of proton movement linked to the association of protein and ligand, giving information on the ionization of groups involved in binding. Biochemical systems characteristically exhibit enthalpy-entropy compensation where increased bonding is offset by an entropic penalty, reducing the magnitude of change in affinity. This also causes a lack of correlation between the free energy of binding (delta G degree) and delta H degree. When characterizing structure-activity relationships (SAR), most groups involved in binding can be detected as contributing to delta H degree, but not to affinity. Large enthalpy changes may reflect a modified binding mode, or protein conformation changes. Thus, delta H degree values may highlight a potential discontinuity in SAR, so that experimental structural data are likely to be particularly valuable in molecular design.
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Affiliation(s)
- W H Ward
- AstraZeneca, R & D Mereside, Alderley Park, Macclesfield, Cheshire, SK10 4TG, UK
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50
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Boraston AB, Creagh AL, Alam MM, Kormos JM, Tomme P, Haynes CA, Warren RA, Kilburn DG. Binding specificity and thermodynamics of a family 9 carbohydrate-binding module from Thermotoga maritima xylanase 10A. Biochemistry 2001; 40:6240-7. [PMID: 11371185 DOI: 10.1021/bi0101695] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The C-terminal family 9 carbohydrate-binding module of xylanase 10A from Thermotoga maritima (CBM9-2) binds to amorphous cellulose, crystalline cellulose, and the insoluble fraction of oat spelt xylan. The association constants (K(a)) for adsorption to insoluble polysaccharides are 1 x 10(5) to 3 x 10(5) M(-1). Of the soluble polysaccharides tested, CBM9-2 binds to barley beta-glucan, xyloglucan, and xylan. CBM9-2 binds specifically to the reducing ends of cellulose and soluble polysaccharides, a property that is currently unique to this CBM. CBM9-2 also binds glucose, xylose, galactose, arabinose, cellooligosaccharides, xylooligosaccharides, maltose, and lactose, with affinities ranging from 10(3) M(-1) for monosaccharides to 10(6) M(-1) for disaccharides and oligosaccharides. Cellooligosaccharides longer than two glucose units do not bind with improved affinity, indicating that cellobiose is sufficient to occupy the entire binding site. In general, the binding reaction is dominated by favorable changes in enthalpy, which are partially compensated by unfavorable entropy changes.
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Affiliation(s)
- A B Boraston
- Protein Engineering Network of Centres of Excellence, Department of Microbiology and Immunology, and The Biotechnology Laboratory, University of British Columbia, Vancouver, British Columbia, V6T 1Z3 Canada
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