Localization and mobility of coenzyme Q in lipid bilayers and membranes

Biofactors. 1999;9(2-4):87-93. doi: 10.1002/biof.5520090202.

Abstract

We have studied the mobility of coenzyme Q (CoQ) in lipid bilayers and mitochondrial membranes in relation to the control of electron transfer activities. A molecular dynamics computer simulation in the vacuum yielded a folded structure for CoQ10, with a length of only 21 A. Using this information we were able to calculate diffusion coefficients in the range of 10(-6) cm2/s in good agreement with those found experimentally by fluorescence quenching of pyrene derivatives. To investigate if CoQ diffusion may represent the rate-limiting step of electron transfer, we reconstituted complexes I and III and assayed the resulting NADH-cytochrome c reductase activity in presence of different CoQ10 levels and at different distances between complexes; the experimental turnovers were higher than the collision frequencies calculated using diffusion coefficients of 10(-9) cm2/s but compatible with values found by us by fluorescence quenching. Since the experimental turnovers are independent of the distance between complexes, we conclude that CoQ diffusion is not rate-limiting for electron transfer.

Publication types

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

MeSH terms

  • Animals
  • Computer Simulation
  • Electron Transport
  • Intracellular Membranes / chemistry
  • Intracellular Membranes / metabolism*
  • Lipid Bilayers / chemistry*
  • Mitochondria / chemistry
  • Mitochondria / metabolism*
  • Models, Molecular
  • Molecular Conformation
  • Ubiquinone / analogs & derivatives
  • Ubiquinone / chemistry*
  • Ubiquinone / metabolism*

Substances

  • Lipid Bilayers
  • Ubiquinone