title: MtGimC, a novel archaeal chaperone related to the eukaryotic chaperonin cofactor GimC/prefoldin.
abstract: Group II chaperonins in the eukaryotic and archaeal cytosol assist in protein folding independently of the GroES-like cofactors of eubacterial group I chaperonins. Recently, the eukaryotic chaperonin was shown to cooperate with the hetero-oligomeric protein complex GimC (prefoldin) in folding actin and tubulins. Here we report the characterization of the first archaeal homologue of GimC, from Methanobacterium thermoautotrophicum. MtGimC is a hexamer of 87 kDa, consisting of two alpha and four beta subunits of high alpha-helical content that are predicted to contain extended coiled coils and represent two evolutionarily conserved classes of Gim subunits. Reconstitution experiments with MtGimC suggest that two subunits of the alpha class (archaeal Gimalpha and eukaryotic Gim2 and 5) form a dimer onto which four subunits of the beta class (archaeal Gimbeta and eukaryotic Gim1, 3, 4 and 6) assemble. MtGimalpha and beta can form hetero-complexes with yeast Gim subunits and MtGimbeta partially complements yeast strains lacking Gim1 and 4. MtGimC is a molecular chaperone capable of stabilizing a range of non-native proteins and releasing them for subsequent chaperonin-assisted folding. In light of the absence of Hsp70 chaperones in many archaea, GimC may fulfil an ATP-independent, Hsp70-like function in archaeal de novo protein folding.
authors.affiliation: Max-Planck-Institut für Biochemie, Department of Cellular Biochemistry, Am Klopferspitz 18A, D-82152 Martinsried, Germany.
authors.forename: M R
authors.initials: MR
authors.lastname: Leroux
authors.forename: M
authors.initials: M
authors.lastname: Fändrich
authors.forename: D
authors.initials: D
authors.lastname: Klunker
authors.forename: K
authors.initials: K
authors.lastname: Siegers
authors.forename: A N
authors.initials: AN
authors.lastname: Lupas
authors.forename: J R
authors.initials: JR
authors.lastname: Brown
authors.forename: E
authors.initials: E
authors.lastname: Schiebel
authors.forename: C M
authors.initials: CM
authors.lastname: Dobson
authors.forename: F U
authors.initials: FU
authors.lastname: Hartl
mesh_terms: D000595:Amino Acid Sequence; D001105:Archaea / Q000737:chemistry*; D015153:Blotting, Western; D002942:Circular Dichroism; D018840:HSP70 Heat-Shock Proteins / Q000737:chemistry; D017014:Methanobacterium / Q000737:chemistry; D018832:Molecular Chaperones / Q000737:chemistry* / Q000502:physiology*; D008969:Molecular Sequence Data; D010802:Phylogeny; D011485:Protein Binding; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D013997:Time Factors
chemical_list: D018840:HSP70 Heat-Shock Proteins; D018832:Molecular Chaperones; D011994:Recombinant Proteins; C112806:prefoldin