Biomaterial Database

Role of second metal ion in establishing active conformations of concanavalin A. 1989

A Sadhu, and J A Magnuson

Biochemistry/Biophysics Program, Washington State University, Pullman 99164-4660.

The stoichiometry of Mn2+ binding to concanavalin A was found to be influenced by temperature, pH, and the presence or absence of saccharide. Demetalized concanavalin A binds one Mn2+ (S1 site) at 5 degrees C, pH 6.5, and two Mn2+ at 25 degrees C (S1 and S2 sites). The association constants for Mn2+ are 6.2 x 10(5) and 3.7 x 10(4) M-1 for the S1 and S2 sites, respectively, at 25 degrees C. Concanavalin A with one Mn2+ bound per monomer remains in an open conformation and exhibits a relatively high water proton relaxation rate. Concanavalin A with two Mn2+ ions remains in a closed conformation characterized by a lower relaxation rate. The rate of binding of the second Mn2+ to concanavalin A as determined by ESR and the rate of conversion of open form to closed form (folding over) as determined by proton relaxation rate measurements gave an identical rate constant of 80.0 +/- 5.8 M-1 h-1 at 17 degrees C. Ca2+, Sr2+, and high levels of methyl alpha-D-mannopyranoside also induce folding of concanavalin A. Ca2+ is not catalytic but stoichiometric in causing the folding. Mn2+ in the S1 site can be displaced by Ni2+, Co2+, and Zn2+, and Mn2+ in the S2 site can be displaced by Ca2+ and Sr2+. Concanavalin A with Ni2+, Co2+, Zn2+, or Mn2+ in the S1 site and Ca2+ or Sr2+ in the S2 site has a higher affinity for methylumbelliferyl alpha-D-mannopyranoside than Ni-Mn-, Co-Mn-, Zn-Mn-, and Cd-Cd-concanavalin A.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008345	Manganese	A trace element with atomic symbol Mn, atomic number 25, and atomic weight 54.94. It is concentrated in cell mitochondria, mostly in the pituitary gland, liver, pancreas, kidney, and bone, influences the synthesis of mucopolysaccharides, stimulates hepatic synthesis of cholesterol and fatty acids, and is a cofactor in many enzymes, including arginase and alkaline phosphatase in the liver. (From AMA Drug Evaluations Annual 1992, p2035)
D008670	Metals	Electropositive chemical elements characterized by ductility, malleability, luster, and conductance of heat and electricity. They can replace the hydrogen of an acid and form bases with hydroxyl radicals. (Grant & Hackh's Chemical Dictionary, 5th ed)	Metal
D008968	Molecular Conformation	The characteristic three-dimensional shape of a molecule.	Molecular Configuration,3D Molecular Structure,Configuration, Molecular,Molecular Structure, Three Dimensional,Three Dimensional Molecular Structure,3D Molecular Structures,Configurations, Molecular,Conformation, Molecular,Conformations, Molecular,Molecular Configurations,Molecular Conformations,Molecular Structure, 3D,Molecular Structures, 3D,Structure, 3D Molecular,Structures, 3D Molecular
D002241	Carbohydrates	A class of organic compounds composed of carbon, hydrogen, and oxygen in a ratio of Cn(H2O)n. The largest class of organic compounds, including STARCH; GLYCOGEN; CELLULOSE; POLYSACCHARIDES; and simple MONOSACCHARIDES.	Carbohydrate
D002413	Cations, Divalent	Positively charged atoms, radicals or groups of atoms with a valence of plus 2, which travel to the cathode or negative pole during electrolysis.	Divalent Cations
D003208	Concanavalin A	A MANNOSE/GLUCOSE binding lectin isolated from the jack bean (Canavalia ensiformis). It is a potent mitogen used to stimulate cell proliferation in lymphocytes, primarily T-lymphocyte, cultures.
D006863	Hydrogen-Ion Concentration	The normality of a solution with respect to HYDROGEN ions; H+. It is related to acidity measurements in most cases by pH	pH,Concentration, Hydrogen-Ion,Concentrations, Hydrogen-Ion,Hydrogen Ion Concentration,Hydrogen-Ion Concentrations
D001665	Binding Sites	The parts of a macromolecule that directly participate in its specific combination with another molecule.	Combining Site,Binding Site,Combining Sites,Site, Binding,Site, Combining,Sites, Binding,Sites, Combining