Three maize leaf ferredoxin:NADPH oxidoreductases vary in subchloroplast location, expression, and interaction with ferredoxin.
In higher plants, ferredoxin (Fd):NADPH oxidoreductase (FNR) catalyzes reduction of NADP+ in the final step of linear photosynthetic electron transport and is also implicated in cyclic electron flow. We have identified three leaf FNR isoenzymes (LFNR1, LFNR2, and LFNR3) in maize (Zea mays) chloroplasts at approximately equivalent concentrations. Fractionation of chloroplasts showed that, while LFNR3 is an exclusively soluble enzyme, LFNR1 is only found at the thylakoid membrane and LFNR2 has a dual location. LFNR1 and LFNR2 were found to associate with the cytochrome b6f complex following its partial purification. We cloned LFNR3 and produced all three isoenzymes as stable, soluble proteins. Measurement of Fd reduction ability showed no significant differences between these recombinant enzymes. Column chromatography revealed variation between the interaction mechanisms of LFNR1 and LFNR2 with Fd, as detected by differential dependence on specific intermolecular salt bridges and variable sensitivity of interactions to changes in pH. A comparison of LFNR transcripts in leaves of plants grown on variable nitrogen regimes revealed that LFNR1 and LFNR2 transcripts are relatively more abundant under conditions of high demand for NADPH. These results are discussed in terms of the functional differentiation of maize LFNR isoenzymes.
Okutani
Satoshi
S
Institute for Protein Research, Osaka University, Suita, Osaka 565-0871, Japan.
Hanke
Guy T
GT
Satomi
Yoshinori
Y
Takao
Toshifumi
T
Kurisu
Genji
G
Suzuki
Akira
A
Hase
Toshiharu
T
D000595:Amino Acid Sequence; D002384:Catalysis; D002736:Chloroplasts / Q000201:enzymology* / Q000378:metabolism; D003001:Cloning, Molecular; D045346:Cytochrome b6f Complex / Q000378:metabolism; D018076:DNA, Complementary / Q000235:genetics; D005287:Ferredoxin-NADP Reductase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005288:Ferredoxins / Q000378:metabolism*; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009584:Nitrogen / Q000494:pharmacology; D010802:Phylogeny; D018515:Plant Leaves / Q000166:cytology / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D021381:Protein Transport; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020524:Thylakoids / Q000378:metabolism; D003313:Zea mays / Q000166:cytology / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism
D018076:DNA, Complementary; D005288:Ferredoxins; D007527:Isoenzymes; D000644:Quaternary Ammonium Compounds; D012333:RNA, Messenger; D045346:Cytochrome b6f Complex; D005287:Ferredoxin-NADP Reductase; D009584:Nitrogen