title: Crystal structure of oxidized cytochrome c(6A) from Arabidopsis thaliana.
abstract: 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 Angstrom 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.
authors.affiliation: Bio-organic Chemistry Laboratory, Graduate School of Bioresource Sciences, Nihon University, Kameino 1866, Fujisawa-shi, Kanagawa 252-8510, Japan.
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Chida
authors.forename: Takeshi
authors.initials: T
authors.lastname: Yokoyama
authors.forename: Fumihiro
authors.initials: F
authors.lastname: Kawai
authors.forename: Aiko
authors.initials: A
authors.lastname: Nakazawa
authors.forename: Hideharu
authors.initials: H
authors.lastname: Akazaki
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Takayama
authors.forename: Takako
authors.initials: T
authors.lastname: Hirano
authors.forename: Kohei
authors.initials: K
authors.lastname: Suruga
authors.forename: Tadashi
authors.initials: T
authors.lastname: Satoh
authors.forename: Seiji
authors.initials: S
authors.lastname: Yamada
authors.forename: Ryu
authors.initials: R
authors.lastname: Kawachi
authors.forename: Satoru
authors.initials: S
authors.lastname: Unzai
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Nishio
authors.forename: Sam-Yong
authors.initials: SY
authors.lastname: Park
authors.forename: Tadatake
authors.initials: T
authors.lastname: Oku
mesh_terms: D017360:Arabidopsis / Q000201:enzymology*; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000235:genetics; D001665:Binding Sites; D018360:Crystallography, X-Ray; D003545:Cysteine / Q000235:genetics / Q000378:metabolism; D045365:Cytochromes c6 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006418:Heme; D008958:Models, Molecular; D010084:Oxidation-Reduction; D017434:Protein Structure, Tertiary; D040681:Structural Homology, Protein
chemical_list: D029681:Arabidopsis Proteins; D045365:Cytochromes c6; D006418:Heme; D003545:Cysteine