A reductase/isomerase subunit of mitochondrial NADH: ubiquinone oxidoreductase (complex I) carries an NADPH and is involved in the biogenesis of the complex

U Schulte, V Haupt, A Abelmann, W Fecke, B Brors, Tim Rasmussen, T Friedrich, H Weiss

Research output: Contribution to journalArticle

52 Citations (Scopus)

Abstract

Respiratory chains of bacteria and mitochondria contain closely related forms of the proton-pumping NADH:ubiquinone oxidoreductase, or complex I. The bacterial complex I consists of 14 subunits, whereas the mitochondrial complex contains some 25 extra subunits in addition to the homologues of the bacterial subunits. One of these extra subunits with a molecular mass of 40 kDa belongs to a heterogeneous family of reductases/isomerases with a conserved nucleotide binding site. We deleted this subunit in Neurospora crassa by gene disruption. In the mutant nuo40, a complex I lacking the 40 kDa subunit is assembled. The mutant complex I does not contain tightly bound NADPH present in wild-type complex I. This NADPH cofactor is not connected to the respiratory electron pathway of complex I. The mutant complex has normal NADH dehydrogenase activity and contains the redox groups known for wild-type complex I, one flavin mononucleotide and four iron-sulfur clusters detectable by electron paramagnetic resonance spectroscopy. In the mutant complex these groups are all readily reduced by NADH. However, the mutant complex is not capable of reducing ubiquinone. A recently described redox group identified in wild-type complex I by UV-visible spectroscopy is not detectable in the mutant complex. We propose that the reductase/isomerase subunit with its NADPH cofactor takes part in the biosynthesis of this new redox group. (C) 1999 Academic Press.

Original languageEnglish
Pages (from-to)569-580
Number of pages12
JournalJournal of Molecular Biology
Volume292
Issue number3
DOIs
Publication statusPublished - 24 Sep 1999

Keywords

  • NADH : ubiquinone oxidoreductase
  • complex I
  • respiratory chain
  • proton-translocation
  • quinoprotein
  • BOVINE HEART-MITOCHONDRIA
  • CYTOCHROME-C-OXIDASE
  • NEUROSPORA-CRASSA MITOCHONDRIA
  • PROTON-TRANSLOCATING NADH
  • ESCHERICHIA-COLI
  • RESPIRATORY-CHAIN
  • SUBMITOCHONDRIAL PARTICLES
  • SACCHAROMYCES-CEREVISIAE
  • PARACOCCUS-DENITRIFICANS
  • INDEPENDENT PATHWAYS
  • NADH
  • ubiquinone oxidoreductase
  • quinoprotein

Cite this