title: PAB is an assembly chaperone that functions downstream of chaperonin 60 in the assembly of chloroplast ATP synthase coupling factor 1.
abstract: The chloroplast ATP synthase, a multisubunit complex in the thylakoid membrane, catalyzes the light-driven synthesis of ATP, thereby supplying the energy for carbon fixation during photosynthesis. The chloroplast ATP synthase is composed of both nucleus- and chloroplast-encoded proteins that have required the evolution of novel mechanisms to coordinate the biosynthesis and assembly of chloroplast ATP synthase subunits temporally and spatially. Here we have elucidated the assembly mechanism of the α3β3γ core complex of the chloroplast ATP synthase by identification and functional characterization of a key assembly factor, PAB (protein in chloroplast atpase biogenesis). PAB directly interacts with the nucleus-encoded γ subunit and functions downstream of chaperonin 60 (Cpn60)-mediated CF1γ subunit folding to promote its assembly into the catalytic core. PAB does not have any recognizable motifs or domains but is conserved in photosynthetic eukaryotes. It is likely that PAB evolved together with the transfer of chloroplast genes into the nucleus to assist nucleus-encoded CF1γ assembly into the CF1 core. Such coordination might represent an evolutionarily conserved mechanism for folding and assembly of nucleus-encoded proteins to ensure proper assembly of multiprotein photosynthetic complexes.
authors.affiliation: Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China; University of Chinese Academy of Sciences, Beijing 100049, China; and.
authors.forename: Juan
authors.initials: J
authors.lastname: Mao
authors.affiliation: Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China;
authors.forename: Wei
authors.initials: W
authors.lastname: Chi
authors.affiliation: Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China;
authors.forename: Min
authors.initials: M
authors.lastname: Ouyang
authors.affiliation: Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China; University of Chinese Academy of Sciences, Beijing 100049, China; and.
authors.forename: Baoye
authors.initials: B
authors.lastname: He
authors.affiliation: State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100086, China.
authors.forename: Fan
authors.initials: F
authors.lastname: Chen
authors.affiliation: Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China; zhanglixin@ibcas.ac.cn.
authors.forename: Lixin
authors.initials: L
authors.lastname: Zhang
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D002384:Catalysis; D020134:Catalytic Domain; D018834:Chaperonin 60 / Q000378:metabolism*; D025222:Chloroplast Proton-Translocating ATPases / Q000235:genetics / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism*; D019286:Endopeptidase K / Q000737:chemistry; D049452:Green Fluorescent Proteins / Q000378:metabolism; D018832:Molecular Chaperones / Q000378:metabolism*; D010641:Phenotype; D010788:Photosynthesis; D018515:Plant Leaves / Q000378:metabolism; D017510:Protein Folding; D020524:Thylakoids / Q000378:metabolism; D020798:Two-Hybrid System Techniques
chemical_list: D029681:Arabidopsis Proteins; D018834:Chaperonin 60; D018832:Molecular Chaperones; C000598505:PAB protein, Arabidopsis; D049452:Green Fluorescent Proteins; D000255:Adenosine Triphosphate; D019286:Endopeptidase K; D025222:Chloroplast Proton-Translocating ATPases
keywords: ATP synthase; Cpn60; assembly; chloroplast