The amino acid sequence in the vicinity of the covalently bound adenylic acid in glutamine synthetase from Escherichia coli.

Under certain conditions of growth, the Escherichiu coli glutamine synthetase is modified by the introduction into the enzyme molecule of covalently bound adenylic acid. This mechanism for modification of the preformed enzyme was discovered independently in this country by Kingdon and Stadtman (1, 2) and in Germany by Holzer et al. (3, 4). An enzyme was described by Kingdon, Shapiro, and Stadtman (5) and by Wulff, Mecke, and Holzer (6) which catalyzes the adenylylation of the glutamine synthetase in the presence of magnesium ions and glutamine, with ATP as the adenylic acid donor. Another enzyme, which catalyzes deadenylylation, has been studied by Shapiro and Stadtman (7), Shapiro (8), and Heihneyer, Battig, and Holzer (9). Kingdon et al. (5) showed that glutamine synthetase can be adenylylated to the extent of 12 5’-adenylyl groups per enzyme molecule. Since E. coli glutamine synthetase has been shown to have a molecular weight of 600,000, with 12 identical subunits (lo), this corresponds to one 5’-adenylic acid per subunit. The 5’-adenylyl group in naturally occurring glutamine synthetase was identified by Shapiro, Kingdon, and Stadtman