title: Three-dimensional structure of NADH: ubiquinone reductase (complex I) from Neurospora mitochondria determined by electron microscopy of membrane crystals.
abstract: NADH: ubiquinone reductase (electron transfer complex I) has been isolated from Neurospora crassa mitochondria as a monodisperse protein-phospholipid-Triton X-100 complex (1:0.04:0.15, by weight). The enzyme is in the monomeric state, has a protein molecular weight of 610,000 and consists of about 25 different subunits. Membrane crystals of the enzyme complex have been prepared by adding mixed phospholipid-Triton X-100 micelles and then removing the Triton by dialysis. Diffraction patterns of the negatively stained membrane crystals extend to about 3.9 nm, with a unit cell size of 19 nm X 38 nm and gamma = 90 degrees. The two-sided plane group packing corresponding to pgg is p22(1)2(1). By combining four sets of tilted views, a low-resolution three-dimensional structure of the protein has been calculated. The structure shows that NADH: ubiquinone reductase extends 15 nm across the membrane, projecting 9 nm from one membrane side and 1 nm from the opposite side. Only about one-third of the total protein mass is located in the membrane. The structure of NADH: ubiquinone reductase is compared with that of ubiquinol: cytochrome c reductase determined by electron microscopy of membrane crystals.
mesh_terms: D002851:Chromatography, High Pressure Liquid; D003460:Crystallization; D004591:Electrophoresis, Polyacrylamide Gel; D008854:Microscopy, Electron; D008928:Mitochondria / Q000201:enzymology*; D008970:Molecular Weight; D016660:NAD(P)H Dehydrogenase (Quinone); D009491:Neurospora / Q000201:enzymology*; D009492:Neurospora crassa / Q000201:enzymology* / Q000648:ultrastructure; D011808:Quinone Reductases
chemical_list: D016660:NAD(P)H Dehydrogenase (Quinone); D011808:Quinone Reductases