title: Metal ions in sugar binding, sugar specificity and structural stability of Spatholobus parviflorus seed lectin.
abstract: Spatholobus parviflorus seed lectin (SPL) is a heterotetrameric lectin, with two α and two β monomers. In the crystal structure of SPL α monomer, two residues at positions 240 and 241 are missing. This region was modeled based on the positional and sequence similarities. The role of metal ions in SPL structure was analyzed by 10 ns molecular dynamics simulation. MD simulations were performed in the presence and absence of metal ions to explain the loss of haemagglutinating property of the lectin due to demetallization. Demetallized structure was found to deviate drastically at the metal binding loop region. Affinity of different sugars like N-acetyl galactosamine (GalNAc), D-galactose and lactose towards the native and demetallized protein was calculated by molecular docking studies. It was found that the sugar binding site got severely distorted in demetallized lectin. Consequently, sugar binding ability of lectin might be decreasing in the demetallized condition. Isothermal titration calorimetric (ITC) analysis of the sugars in the presence of native and demetallized protein confirmed the in silico results. It was observed after molecular dynamics simulations, that significant structural deviations were not caused in the quaternary structure of demetallized lectin. It was confirmed that the structural changes modified the sugar binding ability, as well as sugar specificity of the present lectin. The role of metal ions in sugar binding is described based on the in silico studies and ITC analysis. A comprehensive analysis of the ITC data suggests that the sugar specificity of the metal bound lectin and the loss of sugar specificity due to metal chelation are not linear.
authors: Department of Biotechnology & Microbiology and Inter-University Centre for Bioscience, Kannur University, Thalassery Campus, Palayad 670661, India.
authors: Joseph
authors: J
authors: Abhilash
authors: Kalarickal Vijayan
authors: KV
authors: Dileep
authors: Muthusamy
authors: M
authors: Palanimuthu
authors: Krishnan
authors: K
authors: Geethanandan
authors: Chittalakkotu
authors: C
authors: Sadasivan
authors: Madhathilkovilakath
authors: M
authors: Haridas
mesh_terms: D000116:Acetylgalactosamine / Q000737:chemistry*; D000371:Agglutination; D001665:Binding Sites; D002118:Calcium / Q000737:chemistry*; D002151:Calorimetry; D002413:Cations, Divalent; D056831:Coordination Complexes / Q000737:chemistry*; D007887:Fabaceae / Q000737:chemistry; D005690:Galactose / Q000737:chemistry*; D007785:Lactose / Q000737:chemistry*; D008345:Manganese / Q000737:chemistry*; D062105:Molecular Docking Simulation; D056004:Molecular Dynamics Simulation; D037121:Plant Lectins / Q000737:chemistry*; D011485:Protein Binding; D055503:Protein Multimerization; D055550:Protein Stability; D020836:Protein Structure, Quaternary; D012639:Seeds / Q000737:chemistry; D013816:Thermodynamics
chemical_list: D002413:Cations, Divalent; D056831:Coordination Complexes; D037121:Plant Lectins; D008345:Manganese; D007785:Lactose; D000116:Acetylgalactosamine; D002118:Calcium; D005690:Galactose
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