Thermal denaturation of tryptophan synthase alpha-subunit. Comparison of the values of thermodynamic parameters of unfolding obtained from van't Hoff analysis of CD measurement with those from calorimetry.


Abstract

Thermal denaturation for the wild-type of tryptophan synthase alpha-subunits from E. coli and one of its mutant proteins was followed by CD measurements at various pHs in the alkaline region and the results from van't Hoff analyses of the thermal denaturation curves were compared with those from calorimetry. Although the far-u.v. CD spectra of the thermally denatured proteins differed from those of the completely denatured states in 3.2 M guanidine hydrochloride, the titration curves by denaturants at higher temperatures were not sigmoidal but straight lines, indicating that the cooperative structure of the proteins has been completely destroyed by heating. The ratio of calorimetric enthalpy change to van't Hoff enthalpy change obtained from calorimetric study was unity, indicating that the thermal denaturation of the proteins was a two-state system. The unfolding heat capacity change (delta Cp) of the wild-type protein from van't Hoff analysis of the thermal denaturation curves by CD measurement was estimated to be 2.45 kcal/mol X deg, which was similar to that from calorimetry. The values of unfolding enthalpy change at denaturation temperatures were lower by about 15 kcal/mol compared to those from calorimetry. Study holds ProTherm entries: 11266, 11267, 11268, 11269, 11270, 11271, 11272, 11273, 11274, 11275, 11276, 11277, 11278, 11279, 11280, 11281 Extra Details: additive : EDTA(1 mM), amino acid substitution; enthalpy change; heat capacity change ;,heat denaturation of protein; mutant protein; tryptophan synthase alpha-subunit

Submission Details

ID: xUhTQv5X

Submitter: Connie Wang

Submission Date: April 24, 2018, 8:42 p.m.

Version: 1

Publication Details
Ogasahara K;Yutani K;Suzuki M;Sugino Y,Int. J. Pept. Protein Res. (1984) Thermal denaturation of tryptophan synthase alpha-subunit. Comparison of the values of thermodynamic parameters of unfolding obtained from van't Hoff analysis of CD measurement with those from calorimetry. PMID:6384087
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