Figure 1: Crystal structure of CaTHL.

(a) Amino acid sequence alignment of thiolases. Secondary structure elements are drawn on the basis of reduced form of CaTHL structure and shown with a green-coloured arrow (β-sheet) and blue-coloured helix (α-helix). The ‘regulatory determinant region (RDR)’ and the ‘catalytic cysteine loop’ are shown in orange and blue colour boxes, respectively. Residues involved in enzyme catalysis and CoA binding are indicated by red- and blue-coloured triangles, respectively. Two catalytic cysteine residues, Cys88 and Cys378, involved in a disulfide bond formation are shown as orange-coloured circles, and the disulfide bond is indicated as an orange line. CaTHL, EcTHL and ZrTHL are representations of THL from C. acetobutylicum, E. coli and Z. ramigera, respectively. (b) Tetrameric structure of CaTHL. The tetrameric structure is shown as a ribbon diagram showing one dimmer in blue and orange and the other dimmer in green and salmon. Two tightly interacted dimmers form a tetramer through L-domain. (c) Monomeric structure of CaTHL. A monomeric protein is shown as a ribbon representation in which the N-, C- and L-domains are distinguished with salmon, light blue and orange colours, respectively. The ‘catalytic cysteine loop’ and ‘RDR’ are distinguished with green and magenta colours, respectively, and labelled. The bound-CoA molecule is shown as sphere model, and two catalytic cysteine residues are presented as stick models with green colour.