Redox properties of Arabidopsis cytochrome c6 are independent of the loop extension specific to higher plants

• Published in: Biochimica et biophysica acta. Bioenergetics Vol. 1657; no. 2; pp. 115 - 120
• Main Authors: Wastl, Jürgen, Molina-Heredia, Fernando P, Hervás, Manuel, Navarro, José A, De la Rosa, Miguel A, Bendall, Derek S, Howe, Christopher J
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 2004
• Subjects: amino acid sequences; Arabidopsis; cytochrome c; Cytochrome c6; Laser flash spectroscopy; Protein expression; Redox midpoint potential; redox potential; sequence homology; Spectroscopy; Spectroscopy; cyt c 6; E m; Pc; Arabidopsis; Redox midpoint potential; PSI; p I; Protein expression; Laser flash spectroscopy; Cytochrome c 6
• ISSN: 0005-2728; 1879-2650
• DOI: 10.1016/j.bbabio.2004.04.007

Cytochrome c 6 (cyt c 6) 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 cyt c 6 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 cyt c 6 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.