D-mannose specific lectin. Homotetramer. The mature chain consists of residues 164-281 followed by 30-148. To form a mature chain the precursor undergoes further post-translational modification after removal of the signal sequence; cleavage after Asn at positions 148, 163, and 281 is followed by transposition and ligation (By formation of a new peptide bond) of residues 164-281 and 30-148. 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. Belongs to the leguminous lectin family. Con A (Canavalia ensiformis)