Respiratory cytochrome c oxidase can be efficiently reduced by the photosynthetic redox proteins cytochrome c6 and plastocyanin in cyanobacteria
2005
Navarro, José A. | Durán, Raúl V. | Rosa, Miguel A. de la | Hervás, Manuel
4 pages.-- PMID: 15963511 [PubMed].-- Printed version published on Jul 4, 2005.
Show more [+] Less [-]Plastocyanin and cytochrome c6 are two small soluble electron carriers located in the intrathylacoidal space of cyanobacteria. Although their role as electron shuttle between the cytochrome b6f and photosystem I complexes in the photosynthetic pathway is well established, their participation in the respiratory electron transport chain as donors to the terminal oxidase is still under debate. Here, we present the first time-resolved analysis showing that both cytochrome c6 and plastocyanin can be efficiently oxidized by the aa3 type cytochrome c oxidase in Nostoc sp. PCC 7119. The apparent electron transfer rate constants are ca. 250 and 300 s−1 for cytochrome c6 and plastocyanin, respectively. These constants are 10 times higher than those obtained for the oxidation of horse cytochrome c by the oxidase, in spite of being a reaction thermodynamically more favourable.
Show more [+] Less [-]This research was supported by the Spanish Ministry of Education and Science (Grant BMC2003-0458), Andalusian Government (PAI, CVI-0198) and the European Commission through the Human Potential Programme (Contract HPRN-CT-1999-00095). The authors thank Cristina Albarrán for providing the Nostoc cytochrome c6 samples.
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