title: Scanning transmission electron microscopic study of alpha-ketoglutarate dehydrogenase complex from Escherichia coli.
abstract: The alpha-ketoglutarate dehydrogenase complex was resolved into its three component enzymes: alpha-ketoglutarate dehydrogenase (E1), dihydrolipoyl transsuccinylase (E2), and dihydrolipoyl dehydrogenase. Subcomplexes were prepared in vitro by incubating the resolved E2, a 24-subunit cube-shaped molecule, with E1 (dimeric). The morphology and mass of the subcomplexes were determined by scanning transmission electron microscopy of negatively stained and of freeze-dried specimens. Images of both negative stained and freeze-dried subcomplexes were consistent with E1 binding at or near the midpoints of the edges of the E2 molecule. Mass analysis of the freeze-dried specimen showed that at least 95% of E1 remains in the dimeric state (or as two closely juxtaposed monomers) when it binds to E2.
mesh_terms: D004926:Escherichia coli / Q000201:enzymology*; D007655:Ketoglutarate Dehydrogenase Complex / Q000302:isolation & purification; D007658:Ketone Oxidoreductases / Q000302:isolation & purification; D046911:Macromolecular Substances; D008854:Microscopy, Electron; D008855:Microscopy, Electron, Scanning; D008970:Molecular Weight; D011487:Protein Conformation; D014357:Trypsin
chemical_list: D046911:Macromolecular Substances; D007658:Ketone Oxidoreductases; D007655:Ketoglutarate Dehydrogenase Complex; D014357:Trypsin