The structure of concanavalin A (ConA) has been studied intensively owing to its specific interactions with carbohydrates and its heterometal (CaÂČâș and MnÂČâș) coordination. Most structures from X-ray crystallography have shown ConA as a dimer or tetramer, because the complex formation requires specific crystallization conditions. Here, we reported the monomeric structure of ConA with a resolution of 1.6 Ă , which revealed that metal coordination could trigger sugar-binding ability. The calcium coordination residue, Asn14, changed the orientation of carbohydrate-binding residues and biophysical details, including structural information, providing valuable clues for the development and application of detection kits using ConA.