title: Structure and mechanism of the Rubisco-assembly chaperone Raf1.
abstract: Biogenesis of the photosynthetic enzyme Rubisco, a complex of eight large (RbcL) and eight small (RbcS) subunits, requires assembly chaperones. Here we analyzed the role of Rubisco accumulation factor1 (Raf1), a dimer of ∼40-kDa subunits. We find that Raf1 from Synechococcus elongatus acts downstream of chaperonin-assisted RbcL folding by stabilizing RbcL antiparallel dimers for assembly into RbcL8 complexes with four Raf1 dimers bound. Raf1 displacement by RbcS results in holoenzyme formation. Crystal structures show that Raf1 from Arabidopsis thaliana consists of a β-sheet dimerization domain and a flexibly linked α-helical domain. Chemical cross-linking and EM reconstruction indicate that the β-domains bind along the equator of each RbcL2 unit, and the α-helical domains embrace the top and bottom edges of RbcL2. Raf1 fulfills a role similar to that of the assembly chaperone RbcX, thus suggesting that functionally redundant factors ensure efficient Rubisco biogenesis.
authors.affiliation: Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Martinsried, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Hauser
authors.affiliation: Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Martinsried, Germany.
authors.forename: Javaid Y
authors.initials: JY
authors.lastname: Bhat
authors.affiliation: Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Martinsried, Germany.
authors.forename: Goran
authors.initials: G
authors.lastname: Miličić
authors.affiliation: Gene Center Munich, Ludwig-Maximilians-Universität München, Munich, Germany.
authors.forename: Petra
authors.initials: P
authors.lastname: Wendler
authors.affiliation: Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Martinsried, Germany.
authors.forename: F Ulrich
authors.initials: FU
authors.lastname: Hartl
authors.affiliation: Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Martinsried, Germany.
authors.forename: Andreas
authors.identifier: http://orcid.org/0000-0001-8530-7594
authors.initials: A
authors.lastname: Bracher
authors.affiliation: Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Martinsried, Germany.
authors.forename: Manajit
authors.initials: M
authors.lastname: Hayer-Hartl
mesh_terms: D017360:Arabidopsis / Q000737:chemistry / Q000201:enzymology* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000378:metabolism*; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D008970:Molecular Weight; D011487:Protein Conformation; D055503:Protein Multimerization; D046940:Synechococcus / Q000201:enzymology
chemical_list: D029681:Arabidopsis Proteins; C000598295:RAF1 protein, Arabidopsis