title: NMR studies on the substrate-binding domains of the thermosome: structural plasticity in the protrusion region.
abstract: Group II chaperonins close their cavity with the help of conserved, helical extensions, the so-called protrusions, which emanate from the apical or substrate-binding domains. A comparison of previously solved crystal structures of the apical domains of the thermosome from Thermoplasma acidophilum showed structural plasticity in the protrusion parts induced by extensive packing interactions. In order to assess the influence of the crystal contacts we investigated both the alpha and beta-apical domains (alpha-ADT and beta-ADT) in solution by NMR spectroscopy. Secondary structure assignments and 15N backbone relaxation measurements showed mostly rigid structural elements in the globular parts of the domains, but revealed intrinsic structural disorder and partial helix fraying in the protrusion regions. On the other hand, a beta-turn-motif conserved in archaeal group II chaperonins might facilitate substrate recognition. Our results help us to specify the idea of the open, substrate-accepting state of the thermosome and may provide an additional jigsaw piece in understanding the mode of substrate binding of group II chaperonins.
authors.affiliation: Institut für Organische Chemie und Biochemie II, Technische Universität München, Garching, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Heller
authors.forename: Michael
authors.initials: M
authors.lastname: John
authors.forename: Murray
authors.initials: M
authors.lastname: Coles
authors.forename: Gundula
authors.initials: G
authors.lastname: Bosch
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Baumeister
authors.forename: Horst
authors.initials: H
authors.lastname: Kessler
mesh_terms: D019843:Archaeal Proteins / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D018833:Chaperonins / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D009587:Nitrogen Isotopes / Q000737:chemistry; D019906:Nuclear Magnetic Resonance, Biomolecular; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011522:Protons; D056405:Thermosomes
chemical_list: D019843:Archaeal Proteins; D009587:Nitrogen Isotopes; D011522:Protons; D018833:Chaperonins; D056405:Thermosomes