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Abstract
Lectins are widely distributed proteins having ability of binding selectively and reversibly with carbohydrates moieties and glycoconjugates. Although lectins have been reported from different biological sources, the legume lectins are the best-characterized family of plant lectins. Legume lectins are a large family of homologous proteins with considerable similarity in amino acid sequence and their tertiary structures. Despite having strong sequence conservation, these lectins show remarkable variability in carbohydrate specificity and quaternary structures. The ability of legume lectins in recognizing glycans and glycoconjugates on cells and other intracellular structures make them a valuable research tool in glycomic research. Due to variability in binding with glycans, glycoconjugates and multiple biological functions, legume lectins are the subject of intense research for their diverse application in different fields such as glycobiology, biomedical research and crop improvement. The present review specially focuses on structural and functional characteristics of legume lectins along with their potential areas of application.
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Affiliation(s)
- Rajan Katoch
- Biochemistry Laboratory, Department of Genetics and Plant Breeding, CSKHPKV, Palampur, 176 062 India
| | - Ankur Tripathi
- Biochemistry Laboratory, Department of Genetics and Plant Breeding, CSKHPKV, Palampur, 176 062 India
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2
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Cagnoni AJ, Primo ED, Klinke S, Cano ME, Giordano W, Mariño KV, Kovensky J, Goldbaum FA, Uhrig ML, Otero LH. Crystal structures of peanut lectin in the presence of synthetic β-N- and β-S-galactosides disclose evidence for the recognition of different glycomimetic ligands. ACTA CRYSTALLOGRAPHICA SECTION D-STRUCTURAL BIOLOGY 2020; 76:1080-1091. [PMID: 33135679 DOI: 10.1107/s2059798320012371] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Accepted: 09/08/2020] [Indexed: 11/11/2022]
Abstract
Carbohydrate-lectin interactions are involved in important cellular recognition processes, including viral and bacterial infections, inflammation and tumor metastasis. Hence, structural studies of lectin-synthetic glycan complexes are essential for understanding lectin-recognition processes and for the further design of promising chemotherapeutics that interfere with sugar-lectin interactions. Plant lectins are excellent models for the study of the molecular-recognition process. Among them, peanut lectin (PNA) is highly relevant in the field of glycobiology because of its specificity for β-galactosides, showing high affinity towards the Thomsen-Friedenreich antigen, a well known tumor-associated carbohydrate antigen. Given this specificity, PNA is one of the most frequently used molecular probes for the recognition of tumor cell-surface O-glycans. Thus, it has been extensively used in glycobiology for inhibition studies with a variety of β-galactoside and β-lactoside ligands. Here, crystal structures of PNA are reported in complex with six novel synthetic hydrolytically stable β-N- and β-S-galactosides. These complexes disclosed key molecular-binding interactions of the different sugars with PNA at the atomic level, revealing the roles of specific water molecules in protein-ligand recognition. Furthermore, binding-affinity studies by isothermal titration calorimetry showed dissociation-constant values in the micromolar range, as well as a positive multivalency effect in terms of affinity in the case of the divalent compounds. Taken together, this work provides a qualitative structural rationale for the upcoming synthesis of optimized glycoclusters designed for the study of lectin-mediated biological processes. The understanding of the recognition of β-N- and β-S-galactosides by PNA represents a benchmark in protein-carbohydrate interactions since they are novel synthetic ligands that do not belong to the family of O-linked glycosides.
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Affiliation(s)
- Alejandro J Cagnoni
- Laboratorio de Glicómica Funcional y Molecular, Instituto de Biología y Medicina Experimental, IBYME-CONICET, Vuelta de Obligado 2490, C1428ADN Buenos Aires, Argentina
| | - Emiliano D Primo
- Departamento de Biología Molecular, Universidad Nacional de Río Cuarto, INBIAS-CONICET, Ruta Nacional 36 Km 601, 5800 Río Cuarto, Córdoba, Argentina
| | - Sebastián Klinke
- Fundación Instituto Leloir, IIBBA-CONICET, Avenida Patricias Argentinas 435, C1405BWE Buenos Aires, Argentina
| | - María E Cano
- Departamento de Química Orgánica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Intendente Güiraldes 2160, C1428EHA Buenos Aires, Argentina
| | - Walter Giordano
- Departamento de Biología Molecular, Universidad Nacional de Río Cuarto, INBIAS-CONICET, Ruta Nacional 36 Km 601, 5800 Río Cuarto, Córdoba, Argentina
| | - Karina V Mariño
- Laboratorio de Glicómica Funcional y Molecular, Instituto de Biología y Medicina Experimental, IBYME-CONICET, Vuelta de Obligado 2490, C1428ADN Buenos Aires, Argentina
| | - José Kovensky
- Laboratoire de Glycochimie, des Antimicrobiens et des Agroressources (LG2A)-CNRS UMR 7378, Université de Picardie Jules Verne, 33 Rue Saint Leu, 80039 Amiens CEDEX, France
| | - Fernando A Goldbaum
- Fundación Instituto Leloir, IIBBA-CONICET, Avenida Patricias Argentinas 435, C1405BWE Buenos Aires, Argentina
| | - María Laura Uhrig
- Departamento de Química Orgánica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Intendente Güiraldes 2160, C1428EHA Buenos Aires, Argentina
| | - Lisandro H Otero
- Fundación Instituto Leloir, IIBBA-CONICET, Avenida Patricias Argentinas 435, C1405BWE Buenos Aires, Argentina
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Nascimento KS, Silva MTL, Oliveira MV, Lossio CF, Pinto-Junior VR, Osterne VJS, Cavada BS. Dalbergieae lectins: A review of lectins from species of a primitive Papilionoideae (leguminous) tribe. Int J Biol Macromol 2019; 144:509-526. [PMID: 31857177 DOI: 10.1016/j.ijbiomac.2019.12.117] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Revised: 11/06/2019] [Accepted: 12/14/2019] [Indexed: 01/24/2023]
Abstract
Lectins are (glyco)proteins capable of reversibly binding to specific carbohydrates, thus having various functions and applications. Plant lectins are the best studied, and the Leguminoseae family is highlighted in a number of published works, especially species of the Papilionoideae subfamily. Dalbergieae is one of the tribes in this subfamily comprising 49 genera and over 1300 species. From this tribe, about 26 lectins were studied, among which we can highlight the Arachis hypogaea lectin, widely used in cancer studies. Dalbergieae lectins demonstrate various carbohydrate specificities and biological activities including anti-inflammatory, vasorelaxant, nociceptive, antibacterial, antiviral among others. Structurally, these lectins are quite similar in their three-dimensional folding but present significant differences in oligomerization patterns and in the conservation of carbohydrate-recognition domain. Despite the existence of structural data from some lectins, only sparse literature has reported on this tribe's diversity, not to mention the range of biological effects, determined through specific assays. Therefore, this work will review the most important studies on Dalbergieae lectins and their potential biomedical applications.
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Affiliation(s)
- Kyria Santiago Nascimento
- Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Ceará (UFC), Fortaleza, Ceará, Brazil.
| | - Mayara Torquato Lima Silva
- Departamento de Bioquímica, Universidade Federal de Santa Catarina (UFSC), Florianópolis, Santa Catarina, Brazil
| | - Messias Vital Oliveira
- Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Ceará (UFC), Fortaleza, Ceará, Brazil
| | - Claudia Figueiredo Lossio
- Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Ceará (UFC), Fortaleza, Ceará, Brazil
| | | | - Vinicius Jose Silva Osterne
- Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Ceará (UFC), Fortaleza, Ceará, Brazil
| | - Benildo Sousa Cavada
- Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Ceará (UFC), Fortaleza, Ceará, Brazil.
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Sun Z, Liu Q, Qu G, Feng Y, Reetz MT. Utility of B-Factors in Protein Science: Interpreting Rigidity, Flexibility, and Internal Motion and Engineering Thermostability. Chem Rev 2019; 119:1626-1665. [PMID: 30698416 DOI: 10.1021/acs.chemrev.8b00290] [Citation(s) in RCA: 275] [Impact Index Per Article: 55.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Zhoutong Sun
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, 32 West Seventh Avenue, Tianjin Airport Economic Area, Tianjin 300308, China
| | - Qian Liu
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Ge Qu
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, 32 West Seventh Avenue, Tianjin Airport Economic Area, Tianjin 300308, China
| | - Yan Feng
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Manfred T. Reetz
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, 32 West Seventh Avenue, Tianjin Airport Economic Area, Tianjin 300308, China
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, Germany
- Chemistry Department, Philipps-University, Hans-Meerwein-Strasse 4, 35032 Marburg, Germany
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5
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Touw WG, Joosten RP, Vriend G. Detection of trans-cis flips and peptide-plane flips in protein structures. ACTA CRYSTALLOGRAPHICA. SECTION D, BIOLOGICAL CRYSTALLOGRAPHY 2015; 71:1604-14. [PMID: 26249342 PMCID: PMC4528797 DOI: 10.1107/s1399004715008263] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/04/2015] [Accepted: 04/27/2015] [Indexed: 11/13/2022]
Abstract
A coordinate-based method is presented to detect peptide bonds that need correction either by a peptide-plane flip or by a trans-cis inversion of the peptide bond. When applied to the whole Protein Data Bank, the method predicts 4617 trans-cis flips and many thousands of hitherto unknown peptide-plane flips. A few examples are highlighted for which a correction of the peptide-plane geometry leads to a correction of the understanding of the structure-function relation. All data, including 1088 manually validated cases, are freely available and the method is available from a web server, a web-service interface and through WHAT_CHECK.
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Affiliation(s)
- Wouter G. Touw
- Centre for Molecular and Biomolecular Informatics, Radboud University Medical Center, Geert Grooteplein-Zuid 26-28, 6525 GA Nijmegen, The Netherlands
| | - Robbie P. Joosten
- Department of Biochemistry, Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
| | - Gert Vriend
- Centre for Molecular and Biomolecular Informatics, Radboud University Medical Center, Geert Grooteplein-Zuid 26-28, 6525 GA Nijmegen, The Netherlands
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6
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Pattern Recognition in Legume Lectins to Extrapolate Amino Acid Variability to Sugar Specificity. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014. [DOI: 10.1007/978-3-319-11280-0_13] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
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7
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Maupin KA, Liden D, Haab BB. The fine specificity of mannose-binding and galactose-binding lectins revealed using outlier motif analysis of glycan array data. Glycobiology 2011; 22:160-9. [PMID: 21875884 DOI: 10.1093/glycob/cwr128] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Glycan-binding proteins are commonly used as analytical reagents to detect the levels of specific glycan structures in biological samples. A detailed knowledge of the specificities of glycan-binding proteins is required for properly interpreting their binding data. A powerful technology for characterizing glycan-binding specificity is the glycan array. However, the interpretation of glycan-array data can be difficult due to the complex fine specificities of certain glycan-binding proteins. We developed a systematic approach, called outlier-motif analysis, for extracting fine-specificity information from glycan-array data, and we applied the method to the study of four commonly used lectins: two mannose binders (concanavalin A and Lens culinaris) and two galactose binders (Bauhinia purpurea and peanut agglutinin). The study confirmed the known, primary specificity of each lectin and also revealed new insights into their binding preferences. Lens culinaris's main specificity may be non-terminal, α-linked mannose with a single linkage at its 2' carbon, which is more restricted than previous definitions. We found broader specificity for bauhinea purpurea (BPL) than previously reported, showing that BPL can bind terminal N-acetylgalactosamine (GalNAc) and penultimate β-linked galactose under certain limitations. Peanut agglutinin may bind terminal Galβ1,3Gal, a glycolipid motif, in addition to terminal Galβ1,3GalNAc, a common O-linked glycoprotein motif. These results could be used to more accurately interpret data obtained using these well-studied lectins. Furthermore, this study demonstrates a systematic and general approach for extracting fine-specificity information from glycan-array data.
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Affiliation(s)
- Kevin A Maupin
- Van Andel Research Institute, 333 Bostwick NE, Grand Rapids, MI 49503, USA
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Campana PT, Barbosa LRS, Itri R. Conformational stability of peanut agglutinin using small angle X-ray scattering. Int J Biol Macromol 2011; 48:398-402. [DOI: 10.1016/j.ijbiomac.2010.12.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2010] [Revised: 12/07/2010] [Accepted: 12/09/2010] [Indexed: 11/29/2022]
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Sharma A, Sekar K, Vijayan M. Structure, dynamics, and interactions of jacalin. Insights from molecular dynamics simulations examined in conjunction with results of X-ray studies. Proteins 2010; 77:760-77. [PMID: 19544573 DOI: 10.1002/prot.22486] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Molecular dynamics simulations have been carried out on all the jacalin-carbohydrate complexes of known structure, models of unliganded molecules derived from the complexes and also models of relevant complexes where X-ray structures are not available. Results of the simulations and the available crystal structures involving jacalin permit delineation of the relatively rigid and flexible regions of the molecule and the dynamical variability of the hydrogen bonds involved in stabilizing the structure. Local flexibility appears to be related to solvent accessibility. Hydrogen bonds involving side chains and water bridges involving buried water molecules appear to be important in the stabilization of loop structures. The lectin-carbohydrate interactions observed in crystal structures, the average parameters pertaining to them derived from simulations, energetic contribution of the stacking residue estimated from quantum mechanical calculations, and the scatter of the locations of carbohydrate and carbohydrate-binding residues are consistent with the known thermodynamic parameters of jacalin-carbohydrate interactions. The simulations, along with X-ray results, provide a fuller picture of carbohydrate binding by jacalin than provided by crystallographic analysis alone. The simulations confirm that in the unliganded structures water molecules tend to occupy the positions occupied by carbohydrate oxygens in the lectin-carbohydrate complexes. Population distributions in simulations of the free lectin, the ligands, and the complexes indicate a combination of conformational selection and induced fit.
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Affiliation(s)
- Alok Sharma
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India 560 012
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Gupta G, Vishveshwara S, Surolia A. Stability of dimeric interface in banana lectin: Insight from molecular dynamics simulations. IUBMB Life 2009; 61:252-60. [DOI: 10.1002/iub.162] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Nocek B, Bigelow L, Abdullah J, Joachimiak A. Structure of SO2946 orphan from Shewanella oneidensis shows "jelly-roll" fold with carbohydrate-binding module. JOURNAL OF STRUCTURAL AND FUNCTIONAL GENOMICS 2008; 9:1-6. [PMID: 18566914 PMCID: PMC2678837 DOI: 10.1007/s10969-008-9040-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2008] [Accepted: 05/20/2008] [Indexed: 05/26/2023]
Abstract
The crystal structure of the uncharacterized protein SO2946 from Shewanella oneidensis MR-1 was determined with single-wavelength anomalous diffraction (SAD) and refined to 2.0 A resolution. The SO2946 protein consists of a short helical N-terminal domain and a large C-terminal domain with the "jelly-roll" topology. The protein assembles into a propeller consisting of three C-terminal blades arranged around a central core formed by the N-terminal domains. The function of SO2946 could not be inferred from the sequence since the protein represents an orphan with no sequence homologs, but the protein's structure bears a fold similar to that of proteins containing carbohydrate-binding modules. Features such as fold conservation, the presence of a conserved groove and a metal binding region are indicative that SO2946 may be an enzyme and could be involved in binding carbohydrate molecules.
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Affiliation(s)
- B. Nocek
- Midwest Center for Structural Genomics and Structural Biology Center, Biosciences Division, Argonne National Laboratory, 9700 South Cass Avenue, Building 202, Argonne, IL 60439, USA
| | - L. Bigelow
- Midwest Center for Structural Genomics and Structural Biology Center, Biosciences Division, Argonne National Laboratory, 9700 South Cass Avenue, Building 202, Argonne, IL 60439, USA
| | - J. Abdullah
- Midwest Center for Structural Genomics and Structural Biology Center, Biosciences Division, Argonne National Laboratory, 9700 South Cass Avenue, Building 202, Argonne, IL 60439, USA
| | - A. Joachimiak
- Midwest Center for Structural Genomics and Structural Biology Center, Biosciences Division, Argonne National Laboratory, 9700 South Cass Avenue, Building 202, Argonne, IL 60439, USA
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Suzuki R, Wada J, Katayama T, Fushinobu S, Wakagi T, Shoun H, Sugimoto H, Tanaka A, Kumagai H, Ashida H, Kitaoka M, Yamamoto K. Structural and thermodynamic analyses of solute-binding Protein from Bifidobacterium longum specific for core 1 disaccharide and lacto-N-biose I. J Biol Chem 2008; 283:13165-73. [PMID: 18332142 DOI: 10.1074/jbc.m709777200] [Citation(s) in RCA: 98] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Recently, a gene cluster involving a phosphorylase specific for lacto-N-biose I (LNB; Galbeta1-3GlcNAc) and galacto-N-biose (GNB; Galbeta1-3GalNAc) has been found in Bifidobacterium longum. We showed that the solute-binding protein of a putative ATP-binding cassette-type transporter encoded in the cluster crystallizes only in the presence of LNB or GNB, and therefore we named it GNB/LNB-binding protein (GL-BP). Isothermal titration calorimetry measurements revealed that GL-BP specifically binds LNB and GNB with K(d) values of 0.087 and 0.010 microm, respectively, and the binding process is enthalpy-driven. The crystal structures of GL-BP complexed with LNB, GNB, and lacto-N-tetraose (Galbeta1-3GlcNAcbeta1-3Galbeta1-4Glc) were determined. The interactions between GL-BP and the disaccharide ligands mainly occurred through water-mediated hydrogen bonds. In comparison with the LNB complex, one additional hydrogen bond was found in the GNB complex. These structural characteristics of ligand binding are in agreement with the thermodynamic properties. The overall structure of GL-BP was similar to that of maltose-binding protein; however, the mode of ligand binding and the thermodynamic properties of these proteins were significantly different.
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Affiliation(s)
- Ryuichiro Suzuki
- Department of Biotechnology, the University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
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Affiliation(s)
- M Vijayan
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560012, India.
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Hansia P, Dev S, Surolia A, Vishveshwara S. Insight into the early stages of thermal unfolding of peanut agglutinin by molecular dynamics simulations. Proteins 2007; 69:32-42. [PMID: 17596827 DOI: 10.1002/prot.21512] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Peanut agglutinin is a homotetrameric nonglycosylated protein. The protein has a unique open quaternary structure. Molecular dynamics simulations have been employed to follow the atomistic details of its unfolding at different temperatures. The early events of the deoligomerization of the protein have been elucidated in the present study. Simulation trajectories of the monomer as well as those of the tetramer have been compared and the tetramer is found to be substantially more stable than its monomeric counterpart. The tetramer shows retention of most of its secondary structure but considerable loss of the tertiary structure at high temperature. This observation implies the generation of a molten globule-like intermediate in the later stages of deoligomerization. The quaternary structure of the protein has weakened to a large extent, but none of the subunits are separated. In addition, the importance of the metal-binding to the stability of the protein structure has also been investigated. Binding of the metal ions not only enhances the local stability of the metal-ion binding loop, but also imparts a global stability to the overall structure. The dynamics of different interfaces vary significantly as probed through interface clusters. The differences are substantially enhanced at higher temperatures. The dynamics and the stability of the interfaces have been captured mainly by cluster analysis, which has provided detailed information on the thermal deoligomerization of the protein.
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Affiliation(s)
- Priti Hansia
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560012, Karnataka, India
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Dev S, Surolia A. Dynamic light scattering study of peanut agglutinin: size, shape and urea denaturation. J Biosci 2007; 31:551-6. [PMID: 17301492 DOI: 10.1007/bf02708406] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Peanut agglutinin (PNA)is a homotetrameric protein with a unique open quaternary structure. PNA shows non-two state profile in chaotrope induced denaturation. It passes through a monomeric molten globule like state before complete denaturation (Reddy et al 1999). This denaturation profile is associated with the change in hydrodynamic radius of the native protein. Though the molten globule-like state is monomeric in nature it expands in size due to partial denaturation. The size and shape of the native PNA as well as the change in hydrodynamic radius of the protein during denaturation has been studied by dynamic light scattering (DLS). The generation of two species is evident from the profile of hydrodynamic radii. This study also reveals the extent of compactness of the intermediate state.
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Affiliation(s)
- Sagarika Dev
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560 012, India
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Mitra N, Sinha S, Kini RM, Surolia A. Analysis of the peanut agglutinin molten globule-like intermediate by limited proteolysis. Biochim Biophys Acta Gen Subj 2005; 1725:283-9. [PMID: 16051441 DOI: 10.1016/j.bbagen.2005.04.031] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2005] [Revised: 04/01/2005] [Accepted: 04/26/2005] [Indexed: 11/24/2022]
Abstract
These studies attempt to characterize the molten globule-like intermediate in the unfolding pathway of peanut agglutinin (PNA). PNA is the only known example of a homotetrameric protein that lacks the 2,2,2 or the fourfold symmetry. Previous studies have shown that PNA describes a non two-state unfolding process populated with a clearly defined intermediate. The intermediate is monomeric and has lost most of its tertiary structure and has a substantial amount of secondary structure still intact, thus described as a molten-globule (MG)-like intermediate. It was also shown by isothermal titration calorimetry to bind to lactose and some other ligands with an affinity similar to that of the native protein. This paper describes limited protease cleavage experiments on the intermediate using trypsin and protease V8 for its structural characterization. There are two hydrophobic cores in the PNA subunit. These experiments suggest that in the MG-like intermediate, the second hydrophobic core, near the sugar-binding loop of the protein loosens up. This effect is significantly reduced by the presence of 90% saturating lactose, as deduced by a reduction in cleavage propensity. This is also supported by the gain in the tertiary structure as observed by near-UV CD.
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Affiliation(s)
- Nivedita Mitra
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560012, Karnataka, India
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Roy S, Gupta S, Das S, Sekar K, Chatterji D, Vijayan M. X-ray Analysis of Mycobacterium smegmatis Dps and a Comparative Study Involving Other Dps and Dps-like Molecules. J Mol Biol 2004; 339:1103-13. [PMID: 15178251 DOI: 10.1016/j.jmb.2004.04.042] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2003] [Revised: 04/07/2004] [Accepted: 04/22/2004] [Indexed: 10/26/2022]
Abstract
The structure of the DNA binding protein from starved cells from Mycobacterium smegmatis has been determined in three crystal forms and has been compared with those of similar proteins from other sources. The dodecameric molecule can be described as a distorted icosahedron. The interfaces among subunits are such that the dodecameric molecule appears to have been made up of stable trimers. The situation is similar in the proteins from Escherichia coli and Agrobacterium tumefaciens, which are closer to the M.smegmatis protein in sequence and structure than those from other sources, which appear to form a dimer first. Trimerisation is aided in the three proteins by the additional N-terminal stretches that they possess. The M.smegmatis protein has an additional C-terminal stretch compared to other related proteins. The stretch, known to be involved in DNA binding, is situated on the surface of the molecule. A comparison of the available structures permits a delineation of the rigid and flexible regions in the molecule. The subunit interfaces around the molecular dyads, where the ferroxidation centres are located, are relatively rigid. Regions in the vicinity of the acidic holes centred around molecular 3-fold axes, are relatively flexible. So are the DNA binding regions. The crystal structures of the protein from M.smegmatis confirm that DNA molecules can occupy spaces within the crystal without disturbing the arrangement of the protein molecules. However, contrary to earlier suggestions, the spaces do not need to be between layers of protein molecules. The cubic form provides an arrangement in which grooves, which could hold DNA molecules, criss-cross the crystal.
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Affiliation(s)
- Siddhartha Roy
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560012, India
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