title: Single-particle study of protein assembly.
abstract: A study of protein assembly in solution with single-particle imaging and reconstruction techniques using cryoelectron microscopy is reported. The human glutamine synthetase enzyme, important in brain metabolism, and previously assumed to be assembled into a homogeneous quaternary structure, is found to be heterogeneous, with three oligomeric states that co-exist at room temperature. This result corrects an old structural and kinetic model determined by ensemble averaging techniques that assumed a homogeneous system. Unexpectedly fast protein dissociation kinetics results from a stabilized transition state.
authors.affiliation: Physics Department, University of California, Los Angeles, California 90095, USA.
authors.forename: C H
authors.initials: CH
authors.lastname: Kiang
mesh_terms: D001921:Brain / Q000378:metabolism; D020285:Cryoelectron Microscopy / Q000379:methods*; D005974:Glutamate-Ammonia Ligase / Q000737:chemistry; D006801:Humans; D007700:Kinetics; D011487:Protein Conformation; D020836:Protein Structure, Quaternary; D011506:Proteins / Q000737:chemistry*; D012475:Salmonella / Q000201:enzymology; D013696:Temperature; D013816:Thermodynamics; D014867:Water / Q000737:chemistry
chemical_list: D011506:Proteins; D014867:Water; D005974:Glutamate-Ammonia Ligase