title: Differential interaction of maize root ferredoxin:NADP(+) oxidoreductase with photosynthetic and non-photosynthetic ferredoxin isoproteins.
abstract: In higher plants ferredoxin (Fd):NADP(+) oxidoreductase (FNR) and Fd are each distributed in photosynthetic and non-photosynthetic organs as distinct isoproteins. We have cloned cDNAs for leaf FNR (L-FNR I and L-FNR II) and root FNR (R-FNR) from maize (Zea mays L.), and produced recombinant L-FNR I and R-FNR to study their enzymatic functions through kinetic and Fd-binding analyses. The K(m) value obtained by assay for a diaphorase activity indicated that R-FNR had a 10-fold higher affinity for NADPH than L-FNR I. When we assayed for NADPH-cytochrome c reductase activity using maize photosynthetic Fd (Fd I) and non-photosynthetic Fd (Fd III), the R-FNR showed a marked difference in affinity between these two Fd isoproteins; the K(m) for Fd III was 3.0 microM and that for Fd I was 29 microM. Consistent with this, the dissociation constant for the R-FNR:Fd III complex was 10-fold smaller than that of the R-FNR:Fd I complex. This differential binding capacity was confirmed by an affinity chromatography of R-FNR on Fd-sepharose with stronger binding to Fd III. L-FNR I showed no such differential interaction with Fd I and Fd III. These data demonstrated that R-FNR has the ability to discriminate between these two types of Fds. We propose that the stronger interaction of R-FNR with Fd III is crucial for an efficient electron flux of NADPH-FNR-Fd cascade, thus supporting Fd-dependent metabolism in non-photosynthetic organs.
authors.affiliation: Division of Enzymology, Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka, 565-0871 Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Onda
authors.forename: T
authors.initials: T
authors.lastname: Matsumura
authors.forename: Y
authors.initials: Y
authors.lastname: Kimata-Ariga
authors.forename: H
authors.initials: H
authors.lastname: Sakakibara
authors.forename: T
authors.initials: T
authors.lastname: Sugiyama
authors.forename: T
authors.initials: T
authors.lastname: Hase
mesh_terms: D000595:Amino Acid Sequence; D015153:Blotting, Western; D002846:Chromatography, Affinity; D004591:Electrophoresis, Polyacrylamide Gel; D005287:Ferredoxin-NADP Reductase / Q000235:genetics* / Q000378:metabolism; D005288:Ferredoxins / Q000378:metabolism* / Q000502:physiology; D008969:Molecular Sequence Data; D010788:Photosynthesis / Q000235:genetics* / Q000502:physiology; D018515:Plant Leaves / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D003313:Zea mays / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism
chemical_list: D005288:Ferredoxins; D010940:Plant Proteins; D020033:Protein Isoforms; D011994:Recombinant Proteins; D005287:Ferredoxin-NADP Reductase