title: PAA1, a P-type ATPase of Arabidopsis, functions in copper transport in chloroplasts.
abstract: Copper (Cu) is an essential trace element with important roles as a cofactor in many plant functions, including photosynthesis. However, free Cu ions can cause toxicity, necessitating precise Cu delivery systems. Relatively little is known about Cu transport in plant cells, and no components of the Cu transport machinery in chloroplasts have been identified previously. Cu transport into chloroplasts provides the cofactor for the stromal enzyme copper/zinc superoxide dismutase (Cu/ZnSOD) and for the thylakoid lumen protein plastocyanin, which functions in photosynthetic electron transport from the cytochrome b(6)f complex to photosystem I. Here, we characterized six Arabidopsis mutants that are defective in the PAA1 gene, which encodes a member of the metal-transporting P-type ATPase family with a functional N-terminal chloroplast transit peptide. paa1 mutants exhibited a high-chlorophyll-fluorescence phenotype as a result of an impairment of photosynthetic electron transport that could be ascribed to decreased levels of holoplastocyanin. The paa1-1 mutant had a lower chloroplast Cu content, despite having wild-type levels in leaves. The electron transport defect of paa1 mutants was evident on medium containing <1 micro M Cu, but it was suppressed by the addition of 10 micro M Cu. Chloroplastic Cu/ZnSOD activity also was reduced in paa1 mutants, suggesting that PAA1 mediates Cu transfer across the plastid envelope. Thus, PAA1 is a critical component of a Cu transport system in chloroplasts responsible for cofactor delivery to plastocyanin and Cu/ZnSOD.
authors.affiliation: Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Nara 630-0101, Japan. shikanai@bs.aist-nara.ac.jp
authors.forename: Toshiharu
authors.initials: T
authors.lastname: Shikanai
authors.forename: Patricia
authors.initials: P
authors.lastname: Müller-Moulé
authors.forename: Yuri
authors.initials: Y
authors.lastname: Munekage
authors.forename: Krishna K
authors.initials: KK
authors.lastname: Niyogi
authors.forename: Marinus
authors.initials: M
authors.lastname: Pilon
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D002734:Chlorophyll / Q000378:metabolism; D025222:Chloroplast Proton-Translocating ATPases; D002736:Chloroplasts / Q000187:drug effects / Q000378:metabolism*; D003001:Cloning, Molecular; D003300:Copper / Q000378:metabolism*; D019327:Copper Sulfate / Q000494:pharmacology; D004579:Electron Transport; D007501:Iron / Q000378:metabolism; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D045342:Light-Harvesting Protein Complexes; D008969:Molecular Sequence Data; D009154:Mutation; D010788:Photosynthesis / Q000187:drug effects / Q000235:genetics; D045322:Photosynthetic Reaction Center Complex Proteins / Q000187:drug effects / Q000378:metabolism; D045331:Photosystem I Protein Complex; D010970:Plastocyanin / Q000096:biosynthesis / Q000302:isolation & purification; D017386:Sequence Homology, Amino Acid; D013482:Superoxide Dismutase / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D007527:Isoenzymes; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; D002734:Chlorophyll; D003300:Copper; D010970:Plastocyanin; D007501:Iron; D013482:Superoxide Dismutase; D000251:Adenosine Triphosphatases; D025222:Chloroplast Proton-Translocating ATPases; C477511:PAA1 protein, Arabidopsis; D019327:Copper Sulfate