Metal Ion Interactions with Apo‐Concanavalin A and Some Observations on Metal Ion Requirements and Sugar Binding by Bandeiraea simplicifolia I Lectin

Abstract

AbstractThe kinetics of interaction of Ca2+ ions with M ConA (M = Co2+, Mn2+, Ni2+ and Zn2+) were followed by using the quenching of fluorescence of 4‐methylumbelliferyl‐α‐D‐mannopyranoside when bound to protein. The kinetic data can be interpreted in terms of a mechanism in which a species (MCaP)1 initially formed (constant K1) transforms slowly (k2) to the final form. Values of k1, ΔH1 and ΔS1 and (particularly) k2, ΔH2≠ and ΔS2≠ are very similar for all metals, but the ΔH2≠‐values are much lower than previously reported by other investigators. The kinetics of binding of 4‐methylumbelliferyl‐α‐D‐galactopyranoside to Bandeiraea simplicifolia I lectin were studied by stopped‐flow fluorescence methods. The formation rate constant (∼ 105 M−1 s−1) is similar to that of sugars with other lectins. EDTA removes the sugar binding ability of B. simplicifolia I lectin with t1/2 = 24 min (pH = 7.2, 25°). The addition of Ca2+ ions to apolectin to give a final product appears controlled by a conformational change.