title: CHLORORESPIRATORY REDUCTION 9 is a Novel Factor Required for Formation of Subcomplex A of the Chloroplast NADH Dehydrogenase-Like Complex.
abstract: In vascular plants, the chloroplast NADH dehydrogenase-like (NDH) complex, a homolog of respiratory NADH:quinone oxidoreductase (Complex I), mediates plastoquinone reduction using ferredoxin as an electron donor in cyclic electron transport around PSI in the thylakoid membrane. In angiosperms, chloroplast NDH is composed of five subcomplexes and forms a supercomplex with PSI. The modular assembly of stroma-protruded subcomplex A, which corresponds to the Q module of Complex I, was recently reported. However, the factors involved in the specific assembly steps have not been completely identified. Here, we isolated an Arabidopsis mutant, chlororespiratory reduction 9 (crr9), defective in NDH activity. The CRR9 gene encodes a novel stromal protein without any known functional domains or motifs. CRR9 is highly conserved in cyanobacteria and land plants but not in green algae, which do not have chloroplast NDH. Blue native-PAGE and immunoblot analyses of thylakoid proteins indicated that formation of subcomplex A was impaired in crr9 CRR9 was specifically required for the accumulation of NdhK, a subcomplex A subunit, in NDH assembly intermediates in the stroma. Furthermore, two-dimensional clear native/SDS-PAGE analysis of the stroma fraction indicated that incorporation of NdhM into NDH assembly intermediate complex 400 was impaired in crr9 These results suggest that CRR9 is a novel factor required for the formation of NDH subcomplex A.
authors.affiliation: Department of Botany, Graduate School of Science, Kyoto University, Kyoto, 606-8502 Japan.|CREST, Japan Science and Technology Agency Chiyoda-ku Tokyo, 102-0076 Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yamamoto
authors.affiliation: Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China.
authors.forename: Xiangyuan
authors.initials: X
authors.lastname: Fan
authors.affiliation: Department of Botany, Graduate School of Science, Kyoto University, Kyoto, 606-8502 Japan.
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Sugimoto
authors.affiliation: Department of Bioinformatics, Ritsumeikan University, Kusatsu, Shiga, 525-8577 Japan.|Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Nara, 630-0192 Japan.
authors.forename: Yoichiro
authors.initials: Y
authors.lastname: Fukao
authors.affiliation: Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China.
authors.forename: Lianwei
authors.initials: L
authors.lastname: Peng
authors.affiliation: Department of Botany, Graduate School of Science, Kyoto University, Kyoto, 606-8502 Japan shikanai@pmg.bot.kyoto-u.ac.jp.|CREST, Japan Science and Technology Agency Chiyoda-ku Tokyo, 102-0076 Japan.
authors.forename: Toshiharu
authors.initials: T
authors.lastname: Shikanai
mesh_terms: D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics; D029681:Arabidopsis Proteins / Q000378:metabolism*; D060365:Chloroplast Proteins / Q000378:metabolism*; D002736:Chloroplasts / Q000201:enzymology*; D017124:Conserved Sequence; D000458:Cyanobacteria / Q000235:genetics; D017343:Genes, Plant; D009097:Multienzyme Complexes / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D009245:NADH Dehydrogenase / Q000378:metabolism*; D021122:Protein Subunits / Q000378:metabolism; D020524:Thylakoids / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; C000616111:CRR9 protein, Arabidopsis; D060365:Chloroplast Proteins; D009097:Multienzyme Complexes; D021122:Protein Subunits; D009245:NADH Dehydrogenase
keywords: Arabidopsis; Assembly factor; Chloroplast; Chloroplast NDH; Cyclic electron transport around PSI