1Howard Hughes Medical Institute and Department of Genetics, Yale School of Medicine, New Haven, Connecticut, USA. email: horwich@csbmet.csb.yale.edu
2Department of Crystallography, Birbeck College, London WC1E 7HX, UK. email: h.saibil@mailcryst.bbk.ac.uk
Recent crystal structures of the Thermoplasma acidophilum thermosome and its isolated apical domain suggest that an integral extension of the apical domain encloses the folding-active chaperonin central cavity.
