Chorismate mutase/prephenate dehydratase from Escherichia coli K12. Effect of phenylalanine, NaCl and pH on the protein conformation.
The effects of phenylalanine, NaCl and pH on the conformation of chorismate mutase/prephenate dehydratase have been investigated, using measurements of far and near-ultraviolet circular dichroic spectra and ultraviolet difference spectra. At pH 8.2 in 20 mM Tris-Cl buffer the enzyme was found to contain 10-20% helix and 40-50% beta-structure. There was little or no change in these values on the addition of 1 mM phenylalanine (the allosteric effector) or 0.4 M NaCl or by decreasing the pH to 7.4. Both phenylalanine and NaCl caused significant changes in the conformation of the enzyme. The most prominent of these was the movement of a tryptophan residue into a more hydrophobic environment. There was also a slight perturbation of this tryptophan when the pH was decreased to 7.4. The conformational changes can explain sigmoidal kinetic behaviour observed previously [Gething et al. (1976) Eur. J. Biochem. 71, 317-325].
D000494:Allosteric Regulation; D002942:Circular Dichroism; D004926:Escherichia coli / Q000201:enzymology*; D006836:Hydro-Lyases; D006863:Hydrogen-Ion Concentration; D010649:Phenylalanine; D011302:Prephenate Dehydratase; D011487:Protein Conformation; D012965:Sodium Chloride; D013056:Spectrophotometry, Ultraviolet
D012965:Sodium Chloride; D010649:Phenylalanine; D006836:Hydro-Lyases; D011302:Prephenate Dehydratase