Primary Structure of Escherichia coli Glutamine Synthetase

Evidence that the glutamine synthetase dodecamer from Escherichia coli is comprised of 12 identical subunits of molecular weight 49,000 has been obtained by end group analysis. Application of the carbamylation procedure to the NH2-terminal analysis revealed only serine. The yield was 98% of that expected from a polypeptide of the size proposed for the monomeric species. The following partial sequence of residues at the NH2 terminus of the molecule was elucidated with the aid of automated sequencing equipment: [see PDF for sequence] Hydrolysis of reduced and carboxymethylated glutamine synthetase by carboxypeptidase A yielded quantitative evidence for the following COOH-terminal sequence: -Leu-Tyr-Tyr-Ser-Val-COOH One mole of valine was released per mole of protein, assuming the subunit molecular weight to be 49,000.