title: The photosynthetic cytochrome c550from the diatom Phaeodactylum tricornutum.
abstract: The photosynthetic cytochrome c550from the marine diatom Phaeodactylum tricornutum has been purified and characterized. Cytochrome c550is mostly obtained from the soluble cell extract in relatively large amounts. In addition, the protein appeared to be truncated in the last hydrophobic residues of the C-terminus, both in the soluble cytochrome c550and in the protein extracted from the membrane fraction, as deduced by mass spectrometry analysis and the comparison with the gene sequence. Interestingly, it has been described that the C-terminus of cytochrome c550forms a hydrophobic finger involved in the interaction with photosystem II in cyanobacteria. Cytochrome c550was almost absent in solubilized photosystem II complex samples, in contrast with the PsbO and Psb31 extrinsic subunits, thus suggesting a lower affinity of cytochrome c550for the photosystem II complex. Under iron-limiting conditions the amount of cytochrome c550decreases up to about 45% as compared to iron-replete cells, pointing to an iron-regulated synthesis. Oxidized cytochrome c550has been characterized using continuous wave EPR and pulse techniques, including HYSCORE, and the obtained results have been interpreted in terms of the electrostatic charge distribution in the surroundings of the heme centre.
authors.affiliation: Instituto de Bioquímica Vegetal y Fotosíntesis, Centro de Investigaciones Científicas Isla de la Cartuja, Universidad de Sevilla & CSIC, Américo Vespucio 49, 41092, Sevilla, Spain.
authors.forename: Pilar
authors.initials: P
authors.lastname: Bernal-Bayard
authors.affiliation: Instituto de Bioquímica Vegetal y Fotosíntesis, Centro de Investigaciones Científicas Isla de la Cartuja, Universidad de Sevilla & CSIC, Américo Vespucio 49, 41092, Sevilla, Spain.
authors.forename: Leonor
authors.initials: L
authors.lastname: Puerto-Galán
authors.affiliation: Estación Experimental de Aula Dei, EEAD-CSIC, Zaragoza, Spain.
authors.forename: Inmaculada
authors.identifier: http://orcid.org/0000-0003-3608-4720
authors.initials: I
authors.lastname: Yruela
authors.affiliation: Centro Universitario de la Defensa, Zaragoza, Spain.|Laboratory of Physical Chemistry, ETH Zurich, Zurich, Switzerland.
authors.forename: Inés
authors.initials: I
authors.lastname: García-Rubio
authors.affiliation: Instituto de Bioquímica Vegetal y Fotosíntesis, Centro de Investigaciones Científicas Isla de la Cartuja, Universidad de Sevilla & CSIC, Américo Vespucio 49, 41092, Sevilla, Spain.
authors.forename: Carmen
authors.initials: C
authors.lastname: Castell
authors.affiliation: Instituto de Bioquímica Vegetal y Fotosíntesis, Centro de Investigaciones Científicas Isla de la Cartuja, Universidad de Sevilla & CSIC, Américo Vespucio 49, 41092, Sevilla, Spain.
authors.forename: José M
authors.initials: JM
authors.lastname: Ortega
authors.affiliation: Instituto de Ciencia de Materiales de Aragón, Universidad de Zaragoza & CSIC, Zaragoza, Spain.
authors.forename: Pablo J
authors.initials: PJ
authors.lastname: Alonso
authors.affiliation: Instituto de Bioquímica Vegetal y Fotosíntesis, Centro de Investigaciones Científicas Isla de la Cartuja, Universidad de Sevilla & CSIC, Américo Vespucio 49, 41092, Sevilla, Spain.
authors.forename: Mercedes
authors.initials: M
authors.lastname: Roncel
authors.affiliation: Centro Universitario de la Defensa, Zaragoza, Spain.|Instituto de Ciencia de Materiales de Aragón, Universidad de Zaragoza & CSIC, Zaragoza, Spain.
authors.forename: Jesús I
authors.identifier: http://orcid.org/0000-0002-0536-6074
authors.initials: JI
authors.lastname: Martínez
authors.affiliation: Instituto de Bioquímica Vegetal y Fotosíntesis, Centro de Investigaciones Científicas Isla de la Cartuja, Universidad de Sevilla & CSIC, Américo Vespucio 49, 41092, Sevilla, Spain.
authors.forename: Manuel
authors.initials: M
authors.lastname: Hervás
authors.affiliation: Instituto de Bioquímica Vegetal y Fotosíntesis, Centro de Investigaciones Científicas Isla de la Cartuja, Universidad de Sevilla & CSIC, Américo Vespucio 49, 41092, Sevilla, Spain. jnavarro@ibvf.csic.es.
authors.forename: José A
authors.identifier: http://orcid.org/0000-0002-0536-6074
authors.initials: JA
authors.lastname: Navarro
mesh_terms: D000595:Amino Acid Sequence; D003574:Cytochrome c Group / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D017377:Diatoms / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D008958:Models, Molecular; D008970:Molecular Weight; D010788:Photosynthesis; D045332:Photosystem II Protein Complex / Q000378:metabolism; D055672:Static Electricity
chemical_list: D003574:Cytochrome c Group; D045332:Photosystem II Protein Complex; C031732:cytochrome C-550
keywords: Cytochrome c 550; EPR; Hemeprotein; Phaeodactylum; Photosystem II