Studies on lectins LI. the role of Mn2+ in the activity of the soybean lectin

In contradistinction to previous reports, the lectin of soybeans (Glycine soja) has been shown to retain its erythroagglutinating activity after complete removal of manganese from its molecule. The applied demetallization procedures (dialysis against 0.1 M HCl or 1 M acetic acid and against 0.1 M EDTA followed by dialysis against 1 M acetic acid) had no effect on the stability of the lectin subunit structure, as proved by ultracentrifugation analysis or thin-layer chromatography on Sephadex G-200 Superfine. Affinity electrophoresis' on polyacrylamide gel containing immobilized α-d-galactosyl residues and affinity chromatography on α-d-galactosyl derivative of Separon have shown that the interaction of the demetallized lectin preparations does not differ from that of the native lectin in alkaline media but is decreased in acidic media. Demetallized preparations of soybean lectin can be fully reactivated by dialysis against solutions containing Mn²⁺, Zn²⁺ or Cd²⁺.