passages.id: split_5_test_257_passage
passages.type: progene_text
passages.text: The binding of the essential divalent cation activator Mg2+ and the substrate analog Mg(2+)-AMPCPP to the MutT enzyme to form the quaternary E-Mg(2+)-AMPCPP-Mg2 + complex does not alter the global fold of the enzyme but produces localized small conformational changes at or near the metal and substrate binding sites .