Crystal structure of oxidized cytochrome c 6A from Arabidopsis thaliana

• Published in: FEBS letters 2006-06, Vol.580 (15), p.3763-3768
• Main Authors: Chida, Hirotaka, Yokoyama, Takeshi, Kawai, Fumihiro, Nakazawa, Aiko, Akazaki, Hideharu, Takayama, Yasuhiko, Hirano, Takako, Suruga, Kohei, Satoh, Tadashi, Yamada, Seiji, Kawachi, Ryu, Unzai, Satoru, Nishio, Toshiyuki, Park, Sam-Yong, Oku, Tadatake
• Format: Article
• Language: English
• Subjects: Arabidopsis thaliana; Crystal structure; Cyt; cytochrome; Cytochrome c 6A; Cytochrome c6A; dependence of ΔGunf0 on Gdn-HCl concentration; Electron transfer; Gdn-HCl; Gibbs free energy change for unfolding; guanidine hydrochloride; photosystem I; plastocyanin; PSI; ΔGunf0
• ISSN: 0014-5793; 1873-3468
• DOI: 10.1016/j.febslet.2006.05.067

Compared with algal and cyanobacterial cytochrome c 6, cytochrome c 6A from higher plants contains an additional loop of 12 amino acid residues. We have determined the first crystal structure of cytochrome c 6A from Arabidopsis thaliana at 1.5 Å resolution in order to help elucidate its function. The overall structure of cytochrome c 6A follows the topology of class I c-type cytochromes in which the heme prosthetic group covalently binds to Cys16 and Cys19, and the iron has octahedral coordination with His20 and Met60 as the axial ligands. Two cysteine residues (Cys67 and Cys73) within the characteristic 12 amino acids loop form a disulfide bond, contributing to the structural stability of cytochrome c 6A. Our model provides a chemical basis for the known low redox potential of cytochrome c 6A which makes it an unsuitable electron carrier between cytochrome b 6 f and PSI.