Calcium-induced cooperativity of manganese binding to concanavalin A.
Titrations employing electron spin resonance spectroscopy and equilibrium dialysis studies have revealed that Mn2+ binding to concanavalin A is cooperative in the presence and noncooperative in the absence of Ca2+. The degree of cooperativity increases with increasing pH. Hill coefficients range from 1.4 at pH 5.0 to 1.8 at pH 6.85. In addition to inducing cooperativity in Mn2+ binding, Ca2+ influences the pH dependence and increases the affinity of Mn2+ binding. In contrast to previous suggestions based mostly on work conducted near pH 5, demetallized concanavalin A does bind Ca2+ with an appreciable binding constant. These observations indicate that at physiological pH the role of metal ions in determining functional properties of concanavalin A is different from that suggested by metal binding studies conducted at lower pH values.
D000495:Allosteric Site; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology*; D003208:Concanavalin A / Q000378:metabolism*; D003956:Dialysis; D004578:Electron Spin Resonance Spectroscopy; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008345:Manganese / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D013696:Temperature; D013816:Thermodynamics
D003208:Concanavalin A; D008345:Manganese; D002118:Calcium