title: Crystal structure of a chaperone-bound assembly intermediate of form I Rubisco.
abstract: The form I Rubisco of autotrophic bacteria, algae and plants is a complex of eight large (RbcL) and eight small (RbcS) subunits. It fixes atmospheric CO(2) in the dark reaction of photosynthesis. As shown for the cyanobacterial enzyme, folding of the RbcL subunits is mediated by the GroEL-GroES chaperonin system, and assembly requires the specialized chaperone RbcX, a homodimer of ~15-kDa subunits. Here we present the 3.2-Å crystal structure of a Rubisco assembly intermediate, consisting of the RbcL(8) core with eight RbcX(2) molecules bound. The structure reveals the molecular mechanism by which RbcX(2) mediates oligomeric assembly. Specifically, RbcX(2) provides positional information for proper formation of antiparallel RbcL dimers, thereby preventing RbcL-RbcL misalignment and off-pathway aggregation. The RbcL(8)(RbcX(2))(8) structure also suggests that RbcS functions by stabilizing the '60s loop' of RbcL in the catalytically active conformation.
authors.affiliation: Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Martinsried, Germany. bracher@biochem.mpg.de
authors.forename: Andreas
authors.initials: A
authors.lastname: Bracher
authors.forename: Amanda
authors.initials: A
authors.lastname: Starling-Windhof
authors.forename: F Ulrich
authors.initials: FU
authors.lastname: Hartl
authors.forename: Manajit
authors.initials: M
authors.lastname: Hayer-Hartl
mesh_terms: D017033:Anabaena / Q000235:genetics; D001665:Binding Sites; D018360:Crystallography, X-Ray; D000458:Cyanobacteria / Q000201:enzymology*; D019281:Dimerization; D008958:Models, Molecular; D018832:Molecular Chaperones / Q000737:chemistry* / Q000378:metabolism; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry* / Q000378:metabolism; D012273:Ribulose-Bisphosphate Carboxylase / Q000737:chemistry* / Q000378:metabolism; D046940:Synechococcus / Q000235:genetics
chemical_list: D018832:Molecular Chaperones; D021122:Protein Subunits; D012273:Ribulose-Bisphosphate Carboxylase