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REDOX PROTEINS AS ELECTRON ACCEPTORS FROM CHLOROPHYLL TRIPLET STATE IN LIPID BILAYER VESICLES: KINETICS OF REDUCTION OF MEMBRANE RECONSTITUTED CYTOCHROME c OXIDASE MEDIATED BY 2,5‐DI‐t‐BUTYL BENZOQUINONE AND CYTOCHROME c
Author(s) -
Chamupathi V. G.,
Moezzi D. M.,
Tollin G.
Publication year - 1990
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1990.tb08697.x
Subject(s) - flash photolysis , chemistry , electron transfer , redox , photochemistry , ionic strength , cytochrome , cytochrome c , electron transport chain , electron acceptor , vesicle , cytochrome c oxidase , photosynthetic reaction centre , membrane , kinetics , inorganic chemistry , biochemistry , organic chemistry , reaction rate constant , physics , quantum mechanics , aqueous solution , mitochondrion , enzyme
— Laser flash photolysis was used to determine the kinetics of electron transfer between membrane‐bound triplet chlorophyll ( 3 C), cytochrome c (cyt c) located in the external water phase, and vesicle‐reconstituted cytochrome c oxidase (CCO). 2,5‐Di‐ t ‐butyl benzoquinone (2,5 TBQ) was used as an electron transfer mediator between 3 C and cyt c. A light‐induced cyclic electron transfer sequence between the redox components was observed ( 3 C → 2,5 TBQ → cyt c → CCO → C + ). Under optimum conditions of membrane surface charge and ionic strength, the overall efficiency of CCO reduction (based on 3 C generated by the laser flash) was 14%. Under the anaerobic conditions used, CCO reoxidation (occurring via electron transfer to C + ) was quite slow (halftime approx. 1 s at 75 m M ionic strength). The multicomponent system displayed a high level of stability, as indicated by its ability to undergo many cycles of reduction and reoxidation without any apparent degradation of the components. These results demonstrate the feasibility of constructing complex electron transfer chains, including both soluble and membrane‐bound redox proteins, in artificial lipid bilayers, whose properties can be readily controlled by manipulating parameters such as ionic strength and membrane composition.