Association of ATP: Glutamine Synthetase Adenylyltransferase Activity with the P I Component of the Glutamine Synthetase Deadenylylation System

Abstract

Regulation of glutamine synthetase (EC 6.3.1.2) in Escherichia coli is mediated by adenylylation and deadenylylation of the enzyme. The present studies show that one protein is a common component of both the adenylylation and deadenylylation systems. Thus, the ATP:glutamine synthetase adenylyltransferase, which catalyzes adenylylation of glutamine synthetase, and one of the two proteins required for deadenylylation (the P(I) protein) are inseparable by a variety of fractionation procedures. The adenylyltransferase and P(I)-deadenylylating activities behave as a single protein upon filtration through Agarose A 0.5 gel, and during chromatography on DE32 cellulose and hydroxyapatite columns. They migrate as a single protein band during electrophoresis on polyacrylamide gel and have identical susceptibilities to heat inactivation. These data indicate that the adenylyltransferase and the P(I)-deadenylylation activity are associated with the same protein complex.