Secondary structure predictions of chaperonin proteins. (a) Secondary structure predictions of Thermoplasma acidophilum thermosome alpha subunit ThsA (line Ta_ThsA), human CCTs, mammal CCT8Ls and vertebrate BBSs (lines MKKS, BBS10 and BBS12) compared to the secondary structure description of ThsA (top line 1a6d) determined from its crystal structure (PDB code 1a6d, chain A). Helices are represented as red boxes, beta-strands as yellow boxes and loops as black lines. Secondary structure elements in 1a6d are labeled in succession with numbers (strands) or letters (helices). The first 16 N-terminal residues of ThsA, predicted to contain a strand, are not included in the 1a6d crystal structure (top line). Secondary structure elements in all proteins recognized as homologous to the thermosome chain elements by sequence similarity and positional equivalence are vertically aligned. Blue circles indicate the position of sequence insertions in CCT8L and BBS sequences. (b) The three-dimensional fold of the secondary structure elements in the thermosome structure 1a6d chain A. Red cylinders represent helices and yellow arrows represent strands. Labels (i.e., letters and numbers) correspond to those in panel "a". Elements not predicted in some of the BBS and CCT8L sequences are labeled in gray. The positions of the ATP binding and hydrolysis sites are highlighted in green.