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A comparative structural and functional analysis of cytochrome c M , cytochrome c 6 and plastocyanin from the cyanobacterium Synechocystis sp. PCC 6803
Author(s) -
Molina-Heredia Fernando P,
Balme Alexis,
Hervás Manuel,
Navarro José A,
De la Rosa Miguel A
Publication year - 2002
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(02)02576-0
Subject(s) - plastocyanin , cytochrome , cytochrome b6f complex , cytochrome f , photosystem i , synechocystis , cytochrome c , chemistry , electron transport chain , p700 , cytochrome c1 , cytochrome b , redox , photosystem ii , photochemistry , photosynthesis , biochemistry , coenzyme q – cytochrome c reductase , enzyme , mitochondrion , organic chemistry , mutant , mitochondrial dna , gene
Cytochrome c M is a new c ‐class photosynthetic haem protein whose physiological role is still unknown. It has been proposed previously that cytochrome c M can replace cytochrome c 6 and plastocyanin in transferring electrons between the two membrane complexes cytochrome b 6 – f and photosystem I in organisms growing under stress conditions. The experimental evidence herein provided allows us to discard such a hypothesis. We report a procedure to overexpress cytochrome c M from the cyanobacterium Synechocystis sp. PCC 6803 in Escherichia coli cells in mg quantities. This has allowed us to perform a comparative laser flash‐induced kinetic analysis of photosystem I reduction by the three metalloproteins from Synechocystis . The bimolecular rate constant for the overall reaction is up to 100 times lower with cytochrome c M than with cytochrome c 6 or plastocyanin. In addition, the redox potential value and surface electrostatic potential distribution of cytochrome c M are quite different from those of cytochrome c 6 and plastocyanin. These findings strongly indicate that cytochrome c M cannot be recognised by and interact with the same redox partners as the other two metalloproteins.