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2. An evolutionary analysis of the reaction mechanisms of photosystem I reduction by cytochrome c6 and plastocyanin

Author

Universidad de Sevilla. Departamento de Bioquímica Vegetal y Biología Molecular, Rosa Acosta, Miguel Ángel de la, Navarro Carruesco, José Antonio, Díaz Quintana, Antonio Jesús, Cerda Haynes, Berta de la, Molina Heredia, Fernando Publio, Balme, Alexis, Murdoch, Piedad del Socorro, Díaz Moreno, Irene, Durán, Raúl V., Hervás Morón, Manuel, Universidad de Sevilla. Departamento de Bioquímica Vegetal y Biología Molecular, Rosa Acosta, Miguel Ángel de la, Navarro Carruesco, José Antonio, Díaz Quintana, Antonio Jesús, Cerda Haynes, Berta de la, Molina Heredia, Fernando Publio, Balme, Alexis, Murdoch, Piedad del Socorro, Díaz Moreno, Irene, Durán, Raúl V., and Hervás Morón, Manuel

Abstract

Photosystem I reduction by the soluble metalloproteins cytochrome c6 and plastocyanin, which are alternatively synthesized by some photosynthetic organisms depending on the relative availability of copper and iron, has been investigated in cyanobacteria, green algae and plants. The reaction mechanism is classified in three different types on the basis of the affinity of the membrane complex towards its electron donor protein. The role of electrostatic interactions in forming an intermediate transient complex, as well as the structural and functional similarities of cytochrome c6 and plastocyanin are analysed from an evolutionary point of view. The proposal made is that the heme protein was first “discovered” by nature, when iron was much more abundant on the Earth's surface, and replaced by plastocyanin when copper became available because of the oxidizing conditions of the new atmosphere.

Published
2002

3. An evolutionary analysis of the reaction mechanisms of photosystem I reduction by cytochrome c(6) and plastocyanin

Author

Rosa, Miguel A. de la, Navarro, José A., Díaz-Quintana, Antonio, Cerda, Berta de la, Molina-Heredia, Fernando P., Balme, Alexis, Murdoch, Piedad del S., Díaz-Moreno, Irene, Durán, Raúl V., Hervás, Manuel, Rosa, Miguel A. de la, Navarro, José A., Díaz-Quintana, Antonio, Cerda, Berta de la, Molina-Heredia, Fernando P., Balme, Alexis, Murdoch, Piedad del S., Díaz-Moreno, Irene, Durán, Raúl V., and Hervás, Manuel

Abstract

Photosystem I reduction by the soluble metalloproteins cytochrome c6 and plastocyanin, which are alternatively synthesized by some photosynthetic organisms depending on the relative availability of copper and iron, has been investigated in cyanobacteria, green algae and plants. The reaction mechanism is classified in three different types on the basis of the affinity of the membrane complex towards its electron donor protein. The role of electrostatic interactions in forming an intermediate transient complex, as well as the structural and functional similarities of cytochrome c6 and plastocyanin are analysed from an evolutionary point of view. The proposal made is that the heme protein was first “discovered” by nature, when iron was much more abundant on the Earth's surface, and replaced by plastocyanin when copper became available because of the oxidizing conditions of the new atmosphere.

Published
2002

6. A comparative structural and functional analysis of cytochrome cM, cytochrome c6 and plastocyanin from the cyanobacterium Synechocystis sp. PCC 6803

Author

Molina-Heredia, Fernando P., Balme, Alexis, Hervás, Manuel, Navarro, José A., and De la Rosa, Miguel A.

Subjects
CYTOCHROME c, PLASTOCYANIN
Abstract

Cytochrome cM is a new c-class photosynthetic haem protein whose physiological role is still unknown. It has been proposed previously that cytochrome cM can replace cytochrome c6 and plastocyanin in transferring electrons between the two membrane complexes cytochrome b6–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 cM 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 cM than with cytochrome c6 or plastocyanin. In addition, the redox potential value and surface electrostatic potential distribution of cytochrome cM are quite different from those of cytochrome c6 and plastocyanin. These findings strongly indicate that cytochrome cM cannot be recognised by and interact with the same redox partners as the other two metalloproteins. [Copyright &y& Elsevier]

Published
2002
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