Thermal transition of a mutated dihydrofolate reductase

A mutated dihydrofolate reductase(DHFR), in which Cys 152 of wild DHFR was replaced by Glu and three amino acid residues(Ile-Gln-Ile) were added at C terminal. was obtained by a recombinant DNA method. The thermal transition of the mutant was measured by CD and DSC at pH 7.0 and 7.7 and compared with that of wild DHFR. Analysis of the DSC data revealed that the thermal transition was the three-state one and the thermodynamic functions and mole fractions of native, intermediate and denatured states were calculated.