title: The thermosome: alternating alpha and beta-subunits within the chaperonin of the archaeon Thermoplasma acidophilum.
abstract: The thermosome of the archaeon Thermoplasma acidophilum is composed of two subunits, alpha and beta, which are arranged in two stacked, eight-membered rings. Electron cryo-microscopy in conjunction with image analysis revealed a 4-fold symmetry in the heterooligomeric alpha + beta thermosome isolated from Thermoplasma, but not in the homooligomeric alpha-only thermosome expressed in Escherichia coli. This indicates that alpha and beta-subunits alternate within the rings of the Thermoplasma thermosome rather than forming two different homooligomeric rings. In addition, a small subpopulation of 9-fold symmetric complexes was found among the recombinant alpha-only thermosomes, and a central mass most likely representing bound substrate molecules was observed in about half of the native and recombinant thermosome particles.
authors.affiliation: Abt. für Molekulare Strukturbiologie, Max-Planck-Institut für Biochemie, Martinsried, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Nitsch
authors.forename: M
authors.initials: M
authors.lastname: Klumpp
authors.forename: A
authors.initials: A
authors.lastname: Lupas
authors.forename: W
authors.initials: W
authors.lastname: Baumeister
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry*; D018833:Chaperonins / Q000737:chemistry*; D007053:Ice; D008854:Microscopy, Electron / Q000379:methods; D013822:Thermoplasma / Q000737:chemistry* / Q000201:enzymology / Q000648:ultrastructure
chemical_list: D007053:Ice; D000251:Adenosine Triphosphatases; D018833:Chaperonins