3.2.1.33 | native dimer, native tetramer and the tetramer in complex with acarbose ligand covalently bound to residue D363, occupying subsites -1 to -3. Protein exhibits two different active-site configurations depending on its oligomeric state. The N-terminus of one subunit is located at the active site of the other molecule, resulting in a reshaping of the active site in the tetramer. This is accompanied by a large shift in the flexible loop of amino acids 399-416, creating connected holes inside the tetramer |