title: Structural basis for the isotype-specific interactions of ferredoxin and ferredoxin: NADP+oxidoreductase: an evolutionary switch between photosynthetic and heterotrophic assimilation.
abstract: In higher plants, ferredoxin (Fd) and ferredoxin-NADP+reductase (FNR) are each present as distinct isoproteins of photosynthetic type (leaf type) and non-photosynthetic type (root type). Root-type Fd and FNR are considered to facilitate the electron transfer from NADPH to Fd in the direction opposite to that occurring in the photosynthetic processes. We previously reported the crystal structure of the electron transfer complex between maize leaf FNR and Fd (leaf FNR:Fd complex), providing insights into the molecular interactions of the two proteins. Here we show the 2.49 Å crystal structure of the maize root FNR:Fd complex, which reveals that the orientation of FNR and Fd remarkably varies from that of the leaf FNR:Fd complex, giving a structural basis for reversing the redox path. Root FNR was previously shown to interact preferentially with root Fd over leaf Fd, while leaf FNR retains similar affinity for these two types of Fds. The structural basis for such differential interaction was investigated using site-directed mutagenesis of the isotype-specific amino acid residues on the interface of Fd and FNR, based on the crystal structures of the FNR:Fd complexes from maize leaves and roots. Kinetic and physical binding analyses of the resulting mutants lead to the conclusion that the rearrangement of the charged amino acid residues on the Fd-binding surface of FNR confers isotype-specific interaction with Fd, which brings about the evolutional switch between photosynthetic and heterotrophic redox cascades.
authors.affiliation: Division of Enzymology and Institute for Protein Research, Osaka University, Suita, Osaka, 565-0871, Japan.
authors.forename: Fumio
authors.initials: F
authors.lastname: Shinohara
authors.affiliation: Protein Crystallography, Institute for Protein Research, Osaka University, Suita, Osaka, 565-0871, Japan.
authors.forename: Genji
authors.initials: G
authors.lastname: Kurisu
authors.affiliation: School of Biological and Chemical Sciences, Queen Mary University of London, London, E1 3NU, UK.
authors.forename: Guy
authors.initials: G
authors.lastname: Hanke
authors.affiliation: Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, M13 9PT, UK.
authors.forename: Caroline
authors.initials: C
authors.lastname: Bowsher
authors.affiliation: Division of Enzymology and Institute for Protein Research, Osaka University, Suita, Osaka, 565-0871, Japan.
authors.forename: Toshiharu
authors.initials: T
authors.lastname: Hase
authors.affiliation: Division of Enzymology and Institute for Protein Research, Osaka University, Suita, Osaka, 565-0871, Japan. kimata@yamaguchi-u.ac.jp.|Department of Biological Chemistry, College of Agriculture, Graduate School of Sciences and Technology for Innovation, Yamaguchi University, 1677-1 Yoshida, Yamaguchi, 753-8515, Japan. kimata@yamaguchi-u.ac.jp.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Kimata-Ariga
mesh_terms: D000595:Amino Acid Sequence; D005075:Biological Evolution; D002846:Chromatography, Affinity; D018360:Crystallography, X-Ray; D045304:Cytochromes c / Q000378:metabolism; D005287:Ferredoxin-NADP Reductase / Q000737:chemistry* / Q000378:metabolism; D005288:Ferredoxins / Q000737:chemistry* / Q000378:metabolism; D052836:Heterotrophic Processes; D007700:Kinetics; D008958:Models, Molecular; D016296:Mutagenesis; D010788:Photosynthesis; D018515:Plant Leaves / Q000201:enzymology; D018517:Plant Roots / Q000201:enzymology; D020033:Protein Isoforms / Q000737:chemistry; D003313:Zea mays / Q000201:enzymology
chemical_list: D005288:Ferredoxins; D020033:Protein Isoforms; D045304:Cytochromes c; D005287:Ferredoxin-NADP Reductase
keywords: Electron transfer complex; Ferredoxin; Ferredoxin-NADP+ reductase; Photosynthetic and heterotrophic assimilation; X-ray crystal structure