title: Novel subunit-subunit interactions in the structure of glutamine synthetase.
abstract: We present an atomic model for glutamine synthetase, an enzyme of central importance in bacterial nitrogen metabolism, from X-ray crystallography. The 12 identical subunits are arranged as the carbon atoms in two face-to-face benzene rings, with unusual subunit contacts. Our model, which places the active sites at the subunit interfaces, suggests a mechanism for the main functional role of glutamine synthetase: how the enzyme regulates the rate of synthesis of glutamine in response to covalent modification and feedback inhibition.
mesh_terms: D000227:Adenine Nucleotides; D000494:Allosteric Regulation; D001665:Binding Sites; D002384:Catalysis; D003196:Computer Graphics; D005246:Feedback; D005974:Glutamate-Ammonia Ligase / Q000502:physiology; D046911:Macromolecular Substances; D008958:Models, Molecular; D011487:Protein Conformation; D012486:Salmonella typhimurium; D014961:X-Ray Diffraction
chemical_list: D000227:Adenine Nucleotides; D046911:Macromolecular Substances; D005974:Glutamate-Ammonia Ligase