Conformational changes following Mn(II) binding to demetalized concanavalin A

A temperature-dependent conformational change occurs following the binding of only one Mn(II) to a concanavalin A monomer. This change is independent of Ca(II) near pH 7 and is characterized by an activation energy of 22.3 kcal mol^?1, a value similar to that attributed to a cis-trans peptide isomerization. Two conformations have been detected in magnetic resonance experiments on solvent water protons where spin lattice relaxation times are influenced by bound Mn(II). Both conformations possess saccharide binding activity and Ca(II) stoichiometrically enhances the rate of conversion to the final, more stable conformation.