Evolution of CDT activity in a non-catalytic protein. (a) The reaction
catalyzed by CDT. (b) A phylogenetic tree connecting extant CDTs and related
amino-acid binding proteins. Yellow, affinity for cationic amino acids; grey,
affinity for negatively charged ligands; green, CDT activity. (c) Comparison of
the ligand binding site of AncCDT1 (purple) and the active site of extant
P. aeruginosa CDT (grey). Reprinted by permission from
Springer Nature Nature Chemical Biology
14:542–547, Evolution of cyclohexadienyl dehydratase from an
ancestral solute-binding protein, Clifton BE, Kaczmarski JA, Carr PD, Gerth ML,
Tokuriki N, Jackson CJ.