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Studies on the structure of nadh-ubiquinone oxidoreductase complex - topography of the subunits of the iron-sulfur flavoprotein component

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Overview

authors

  • Han, A. L.
  • Yagi, Takao
  • Hatefi, Y.

publication date

  • December 1988

journal

  • Archives of Biochemistry and Biophysics  Journal

abstract

  • A catalytic component of the bovine mitochondrial NADH:ubiquinone oxidoreductase complex (Complex I) is a soluble NADH dehydrogenase iron-sulfur flavoprotein (FP). FP is composed of three subunits of Mr 51,000, 24,000, and 9,000, and contains FMN and two iron-sulfur clusters. Previous studies by others with the use of various chemical probes had suggested that, except for an access for NADH to the 51-kDa subunit, the FP polypeptides are buried within Complex I and shielded from the medium. In the present study, monospecific antibodies were raised to each of the three FP subunits, and used in conjunction with Complex I, submitochondrial particles (SMP), mitoplasts, and intact mitochondria as sources of antigens. Results of enzyme-linked immunosorbent assays and 125I-protein A labeling experiments indicated that epitopes from the 51-, 24-, and 9-kDa subunits of FP are exposed to the medium in Complex I and SMP, but not in mitoplasts and mitochondria. Appropriate enzymatic assays showed that none of the antibodies inhibited the NADH dehydrogenase activity of isolated FP or the NADH oxidase activity of SMP. These results have been discussed in relation to the structure of Neurospora Complex I deduced from membrane crystals of the isolated enzyme complex by Leonard et al. [K. Leonard, H. Haiker, and H. Weiss (1987) J. Mol. Biol. 194, 277-286].

subject areas

  • Animals
  • Antibody Formation
  • Antigen-Antibody Reactions
  • Binding Sites
  • Cattle
  • Electrophoresis, Polyacrylamide Gel
  • Enzyme-Linked Immunosorbent Assay
  • Epitopes
  • Flavoproteins
  • Immunoblotting
  • Iron-Sulfur Proteins
  • Metalloproteins
  • Mitochondria, Heart
  • NAD(P)H Dehydrogenase (Quinone)
  • Protein Conformation
  • Quinone Reductases
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Identity

International Standard Serial Number (ISSN)

  • 0003-9861

Digital Object Identifier (DOI)

  • 10.1016/0003-9861(88)90055-0

PubMed ID

  • 2463782
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Additional Document Info

start page

  • 490

end page

  • 496

volume

  • 267

issue

  • 2

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