Open AccessKinetics of electron transfer between plastocyanin and the soluble Cu A domain of cyanobacterial cytochrome c oxidase
Author(s) -
Paumann Martina,
Bernroitner Margit,
Lubura Borjana,
Peer Michael,
Jakopitsch Christa,
Furtmüller Paul G.,
Peschek Günter A.,
Obinger Christian
Publication year - 2004
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1016/j.femsle.2004.09.003
Subject(s) - plastocyanin , chemistry , electron transfer , electron transport chain , cytochrome , cytochrome b6f complex , cytochrome c oxidase , synechocystis , cytochrome f , copper protein , cytochrome c , photosystem i , photochemistry , photosynthesis , biochemistry , copper , photosystem ii , enzyme , organic chemistry , mutant , mitochondrion , gene
It has been shown that efficient functioning of photosynthesis and respiration in the cyanobacterium Synechocystis PCC 6803 requires the presence of either cytochrome c 6 or plastocyanin. In order to check whether the blue copper protein plastocyanin can act as electron donor to cytochrome c oxidase, we investigated the intermolecular electron transfer kinetics between plastocyanin and the soluble Cu A domain (i.e. the donor binding and electron entry site) of subunit II of the aa 3 ‐type cytochrome c oxidase from Synechocystis . Both copper proteins were expressed heterologously in Escherichia coli . The forward and the reverse electron transfer reactions were studied yielding apparent bimolecular rate constants of (5.1 ± 0.2) × 10 4 M −1 s −1 and (8.5 ± 0.4) × 10 5 M −1 s −1 , respectively (20 mM phosphate buffer, pH 7). This corresponds to an apparent equilibrium constant of 0.06 in the physiological direction (reduction of Cu A ), which is similar to K eq values calculated for the reaction between c ‐type cytochromes and the soluble fragments of other Cu A domains. The potential physiological role of plastocyanin in cyanobacterial respiration is discussed.