Functional coupling of PSST and ND1 subunits in NADH:ubiquinone oxidoreductase established by photoaffinity labeling

Biochim Biophys Acta. 2001 Jul 2;1506(1):79-87. doi: 10.1016/s0005-2728(01)00183-9.


NADH:ubiquinone oxidoreductase (complex I) is the first, largest and most complicated enzyme of the mitochondrial electron transport chain. Photoaffinity labeling with the highly potent and specific inhibitor trifluoromethyldiazirinyl-[(3)H]pyridaben ([(3)H]TDP) labels only the PSST and ND1 subunits of complex I in electron transport particles. PSST is labeled at a high-affinity site responsible for inhibition of enzymatic activity while ND1 is labeled at a low-affinity site not related to enzyme inhibition. In this study we found, as expected, that 13 complex I inhibitors decreased labeling at the PSST site without effect on ND1 labeling. However, there were striking exceptions where an apparent interaction was found between the PSST and ND1 subunits: preincubation with NADH increases PSST labeling and decreases ND1 labeling; the very weak complex I inhibitor 1-methyl-4-phenylpyridinium ion (MPP(+)) and the semiquinone analogue stigmatellin show the opposite effect with increased labeling at ND1 coupled to decreased labeling at PSST in a concentration- and time-dependent manner. MPP(+), stigmatellin and ubisemiquinone have similarly positioned centers of highly negative and positive electrostatic potential surfaces. Perhaps the common action of MPP(+) and stigmatellin on the functional coupling of the PSST and ND1 subunits is initiated by binding at a semiquinone binding site in complex I.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • 1-Methyl-4-phenylpyridinium / chemistry
  • 1-Methyl-4-phenylpyridinium / pharmacology
  • Binding Sites
  • Electron Transport Complex I
  • Enzyme Inhibitors / pharmacology
  • Enzyme Stability
  • Hot Temperature
  • Molecular Structure
  • Multienzyme Complexes / chemistry
  • NAD / pharmacology
  • NADH, NADPH Oxidoreductases / antagonists & inhibitors
  • NADH, NADPH Oxidoreductases / chemistry*
  • Photoaffinity Labels
  • Polyenes / chemistry
  • Polyenes / pharmacology
  • Pyridazines / pharmacology
  • Rotenone / pharmacology
  • Structure-Activity Relationship
  • Tritium
  • Ubiquinone / analogs & derivatives*
  • Ubiquinone / pharmacology


  • Enzyme Inhibitors
  • Multienzyme Complexes
  • Photoaffinity Labels
  • Polyenes
  • Pyridazines
  • Rotenone
  • NAD
  • Tritium
  • Ubiquinone
  • pyridaben
  • 2,3-dimethoxy-5-methyl-6-decyl-1,4-benzoquinone
  • stigmatellin
  • NADH oxidase
  • NADH, NADPH Oxidoreductases
  • Electron Transport Complex I
  • 1-Methyl-4-phenylpyridinium