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Free keywords:
Chaperonin; Thermosome; Thermoplasma acidophilum; Apical domain; Crystal structure.; Group-ii chaperonins; Archaeal chaperonin; Folding machine; Binding domains; Ef-tu; Protein; Groel; Cct; Conformation; Subunits.; Molecular Biology & Genetics in Current Contents(R)/Life Sciences.
Abstract:
The crystal structure of the alpha alpha-apical domain of the thermosome, an archaeal group II chaperonin from Thermoplasma acidophilum, has been determined at 2.8 Angstrom resolution. The structure shows an invariant globular core from which a 25 Angstrom long protrusion emanates, composed of an elongated a-helix (H10) and a long extended stretch consisting of residues GluB245-ThrB253. A comparison with previous apical domain structures reveals a large segmental displacement of the protruding part of helix H10 via the hinge GluB276-ValB278. The region comprising residues GluB245-ThrB253 adopts an extended beta-like conformation rather than the alpha-helix seen in the alpha-apical domain. Consequently, it appears that the protrusions of the apical domains from group II chaperonins might assume variety of context-dependent conformations during an open, substrate-accepting state of the chaperonin. Sequence variations in the protrusion regions that are found in the eukaryotic TRiC/CCT subunits may provide different structural propensities and hence serve different roles in substrate recognition. (C) 2000 Academic Press. [References: 40]
