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Localization and mobility of coenzyme Q in lipid bilayers and membranes
Author(s) -
Lenaz Giorgio,
Fato Romana,
Di Bernardo Salvatore,
Jarreta Diana,
Costa Angela,
Genova Maria Luisa,
Castelli Giovanna Parenti
Publication year - 1999
Publication title -
biofactors
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.204
H-Index - 94
eISSN - 1872-8081
pISSN - 0951-6433
DOI - 10.1002/biof.5520090202
Subject(s) - coenzyme q – cytochrome c reductase , electron transfer , chemistry , quenching (fluorescence) , diffusion , electron transport chain , pyrene , membrane , limiting , fluorescence , cytochrome c , analytical chemistry (journal) , biophysics , photochemistry , biochemistry , thermodynamics , mitochondrion , organic chemistry , physics , biology , mechanical engineering , engineering , quantum mechanics
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.