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].[1]References
- Chorismate mutase/prephenate dehydratase from Escherichia coli K12. Effect of phenylalanine, NaCl and pH on the protein conformation. Gething, M.J., Davidson, B.E. Eur. J. Biochem. (1978) [Pubmed]
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