D-mannose-specific lectin. Equilibrium between homodimer and homotetramer. The mature chain consists of residues 164-281 followed by residues 30-148. Concanavalin A-like lectins of the Diocleinae subtribe undergo proteolytic processing referred to as circular permutation. The propeptide is split into an N-terminal and a C-terminal part, the gamma and beta chain, respectively. These are then religated in beta-gamma order to form the mature alpha chain. The beta and gamma chains can often be detected in cell extracts. Binds one manganese (or another transition metal) ion and one calcium ion. The metal ions are essential for the saccharide-binding and cell-agglutinating activities. Several isolectin forms may exist. Belongs to the leguminous lectin family.