title: Higher order structure contributes to specific differences in redox potential and electron transfer efficiency of root and leaf ferredoxins.
abstract: Plant type ferredoxin (Fd) is a small [2Fe-2S] cluster containing electron-transfer protein with a highly negative redox potential. Higher plants contain different iso-protein types of Fd in roots and leaves, reflecting the difference in redox cascades between these two tissues. We have combined subdomains of leaf and root Fds in recombinant chimeras, to examine structural effects and the relationship between groups of residues on redox potential, electron transfer, and protein-protein interactions. All chimeras had redox potentials that were intermediate to the wild type leaf and root Fds. Surprisingly, the largest differences resulted from exchange of the N-terminus, the region farthest from the redox center. Homology modeling and energy minimization calculations suggest that the N-terminal chimeras may indirectly influence redox potentials by structurally perturbing the active site. Measurements of electron transport and protein interaction indicate that synergistic interaction between the C- and N-terminal of root Fd bestows a specific high affinity for accepting electrons in the root type electron cascade, and that there is discrimination against photosynthetic electron donation to root Fd based on the C-terminus of the molecule. Taken together, the experimental and computational studies support a model in which higher order structure contributes to iso-protein specific interaction and electron-transfer properties.
authors.affiliation: Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Ping
authors.initials: P
authors.lastname: Gou
authors.forename: Guy T
authors.initials: GT
authors.lastname: Hanke
authors.forename: Yoko
authors.initials: Y
authors.lastname: Kimata-Ariga
authors.forename: Daron M
authors.initials: DM
authors.lastname: Standley
authors.forename: Atsushi
authors.initials: A
authors.lastname: Kubo
authors.forename: Isao
authors.initials: I
authors.lastname: Taniguchi
authors.forename: Haruki
authors.initials: H
authors.lastname: Nakamura
authors.forename: Toshiharu
authors.initials: T
authors.lastname: Hase
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D002846:Chromatography, Affinity; D004579:Electron Transport; D005288:Ferredoxins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D015870:Gene Expression; D007501:Iron / Q000737:chemistry / Q000378:metabolism; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D010084:Oxidation-Reduction; D010802:Phylogeny; D018515:Plant Leaves / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013455:Sulfur / Q000737:chemistry / Q000378:metabolism
chemical_list: D005288:Ferredoxins; D011994:Recombinant Proteins; D013455:Sulfur; D007501:Iron