Stability of oxidized Escherichia coli thioredoxin and its dependence on protonation of the aspartic acid residue in the 26 position.
The effects of pH in the range 6.0-8.0 on the thermodynamics of the reversible thermal unfolding of Escherichia coli thioredoxin in the oxidized state have been determined over a range of concentrations using differential scanning calorimetry. The thermal denaturation indicated an inverse temperature dependence on concentration. The data were shown to fit a model based on dimerization of both the native and denatured states of the protein. The degree of dimerization of both states was found to be pH dependent. The previously described importance of protonation of the anomalously titrating aspartic acid 26 residue [Langsetmo, K., Fuchs, J., & Woodward, C. (1991) Biochemistry 30 ,7603-7609] was apparently verified by the agreement between the experimentally determined delta delta Gzerod and the calculated delta delta GzeroH in the pH range 7.0-8.0.
Department of Chemistry, Yale University, New Haven, Connecticut 06511.
J E
JE
Ladbury
R
R
Wynn
H W
HW
Hellinga
J M
JM
Sturtevant
D001224:Aspartic Acid / Q000737:chemistry*; D002152:Calorimetry, Differential Scanning; D004355:Drug Stability; D004926:Escherichia coli / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D046911:Macromolecular Substances; D010084:Oxidation-Reduction; D011489:Protein Denaturation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D011522:Protons; D013816:Thermodynamics; D013879:Thioredoxins / Q000737:chemistry* / Q000378:metabolism
D046911:Macromolecular Substances; D011522:Protons; D001224:Aspartic Acid; D013879:Thioredoxins