Localization and mobility of coenzyme Q in lipid bilayers and membranes

Article type: Research Article

Authors: Lenaz, Giorgio^; | Fato, Romana | Di Bernardo, Salvatore | Jarreta, Diana | Costa, Angela | Genova, Maria Luisa | Parenti Castelli, Giovanna

Affiliations: Dipartimento di Biochimica “G. Moruzzi”, Università di Bologna, Via Irnerio 48, 40126 Bologna, Italy

Note: [] Corresponding author: Giorgio Lenaz, Dipartimento di Biochimica “G. Moruzzi”, Università di Bologna, Via Irnerio 48, 40126 Bologna, Italy. Tel.: +39 051 351229; Fax: +39 051 351217; E‐mail: lenaz@ biocfarm.unibo.it.

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 CoQ_{10}, with a length of only 21 Å. Using this information we were able to calculate diffusion coefficients in the range of 10^{-6} cm^{2}/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 CoQ_{10 } levels and at different distances between complexes; the experimental turnovers were higher than the collision frequencies calculated using diffusion coefficients of 10^{-9} cm^{2}/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.

Journal: Biofactors, vol. 9, no. 2-4, pp. 87-93, 1999