Adenosine triphosphate: glutamine synthetase adenylyltransferase of Escherichia coli: two active molecular forms

Two active forms of purified ATP:glutamine synthetase adenylyl-transferase from Escherichia coli are apparent on polyacrylamide gel electrophoresis at pH 8. The slower migrating component, which is identical to the P(I)-protein fraction of the glutamine synthetase deadenylylating enzyme system, has S(20.w) congruent with 5.1 S and a molecular weight of about 130,000. The more rapidly migrating adenylyltransferase component has S(20.w) congruent with 4.0 S and a molecular weight of about 70,000. During storage at 4 degrees C, the larger adenylyltransferase component (P(I)) converts to the smaller active unit with a concomitant loss of both P(I) deadenylylating activity and soluble protein. It is concluded that the low-molecular weight form of the adenylyltransferase is a subunit of the deadenylylating P(I)-protein.