title: Interaction of photosystem I from Phaeodactylum tricornutum with plastocyanins as compared with its native cytochrome c6: Reunion with a lost donor.
abstract: In the Phaeodactylum tricornutum alga, as in most diatoms, cytochrome c6 is the only electron donor to photosystem I, and thus they lack plastocyanin as an alternative electron carrier. We have investigated, by using laser-flash absorption spectroscopy, the electron transfer to Phaeodactylum photosystem I from plastocyanins from cyanobacteria, green algae and plants, as compared with its own cytochrome c6. Diatom photosystem I is able to effectively react with eukaryotic acidic plastocyanins, although with less efficiency than with Phaeodactylum cytochrome c6. This efficiency, however, increases in some green alga plastocyanin mutants mimicking the electrostatics of the interaction site on the diatom cytochrome. In addition, the structure of the transient electron transfer complex between cytochrome c6 and photosystem I from Phaeodactylum has been analyzed by computational docking and compared to that of green lineage and mixed systems. Taking together, the results explain why the Phaeodactylum system shows a lower efficiency than the green systems, both in the formation of the properly arranged [cytochrome c6-photosystem I] complex and in the electron transfer itself.
authors.affiliation: Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla and CSIC, Américo Vespucio 49, 41092 Sevilla, Spain.
authors.forename: Pilar
authors.initials: P
authors.lastname: Bernal-Bayard
authors.affiliation: Joint BSC-CRG-IRB Research Program in Computational Biology, Life Sciences Department, Barcelona Supercomputing Center, Barcelona 08034, Spain.
authors.forename: Chiara
authors.initials: C
authors.lastname: Pallara
authors.affiliation: Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla and CSIC, Américo Vespucio 49, 41092 Sevilla, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Carmen Castell
authors.affiliation: Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla and CSIC, Américo Vespucio 49, 41092 Sevilla, Spain.
authors.forename: Fernando P
authors.initials: FP
authors.lastname: Molina-Heredia
authors.affiliation: Joint BSC-CRG-IRB Research Program in Computational Biology, Life Sciences Department, Barcelona Supercomputing Center, Barcelona 08034, Spain.
authors.forename: Juan
authors.initials: J
authors.lastname: Fernández-Recio
authors.affiliation: Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla and CSIC, Américo Vespucio 49, 41092 Sevilla, Spain.
authors.forename: Manuel
authors.initials: M
authors.lastname: Hervás
authors.affiliation: Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla and CSIC, Américo Vespucio 49, 41092 Sevilla, Spain. Electronic address: jnavarro@ibvf.csic.es.
authors.forename: José A
authors.initials: JA
authors.lastname: Navarro
mesh_terms: D045365:Cytochromes c6 / Q000737:chemistry / Q000378:metabolism*; D007700:Kinetics; D062105:Molecular Docking Simulation; D010788:Photosynthesis; D045331:Photosystem I Protein Complex / Q000737:chemistry / Q000378:metabolism*; D010970:Plastocyanin / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D058009:Stramenopiles / Q000378:metabolism* / Q000502:physiology
chemical_list: D045365:Cytochromes c6; D045331:Photosystem I Protein Complex; D010970:Plastocyanin
keywords: Computational docking; Cytochrome c(6); Electron transfer; Laser flash photolysis; Phaeodactylum; Photosystem I; Plastocyanin