title: Redox properties of Arabidopsis cytochrome c6 are independent of the loop extension specific to higher plants.
abstract: Cytochrome c6 (cytc6) from Arabidopsis differs from the cyanobacterial and algal homologues in several redox properties. It is possible that these differences might be due to the presence of a 12 amino acid residue loop extension common to higher plant cytc6 proteins. However, homology modelling suggests this is not the case. We report experiments to test if differences in biochemical properties could be due to this extension. Analysis of mutant forms of Arabidopsis cytc6 in which the entire extension was lacking, or a pair of cysteine residues in the extension had been exchanged for serine, revealed no significant effect of these changes on either the redox potential of the haem group or the reactivity towards Photosystem I (PSI). We conclude that the differences in properties are due to more subtle unidentified differences in structure, and that the sequence extension in the higher plant proteins has a function yet to be identified.
authors.affiliation: Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QW, UK. jw312@mole.bio.cam.ac.uk
authors.forename: Jürgen
authors.initials: J
authors.lastname: Wastl
authors.forename: Fernando P
authors.initials: FP
authors.lastname: Molina-Heredia
authors.forename: Manuel
authors.initials: M
authors.lastname: Hervás
authors.forename: José A
authors.initials: JA
authors.lastname: Navarro
authors.forename: Miguel A
authors.initials: MA
authors.lastname: De la Rosa
authors.forename: Derek S
authors.initials: DS
authors.lastname: Bendall
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Howe
mesh_terms: D017360:Arabidopsis / Q000201:enzymology*; D001483:Base Sequence; D045365:Cytochromes c6 / Q000378:metabolism*; D017931:DNA Primers; D007526:Isoelectric Point; D010084:Oxidation-Reduction
chemical_list: D045365:Cytochromes c6; D017931:DNA Primers