Abstract

The reversible thermal unfolding of wild type and mutant dihydrofolate reductase (DHFR) from E. coli has been previously studied by optical spectroscopy. This information indicated the presence of molten globule type intermediates as well as irreversible type melting. In order to further explore these results, a series of DSC experiments at a number of different pHs were conducted using the C85S/C152E DHFR mutant. The lack of the disulfide bonds, that are present in the wild-type, greatly increased the reversibility of the thermal denaturation. It was also found that the protein achieves maximum stability at pH 7.0 with destabilization occurring above and below this value. Presently, experiments are being conducted at high salt concentrations in an attempt to further stabilize possible intermediates. Circular dichroism (CD) at reduced concentrations will also be performed to investigate the concentration dependent behavior found in the DSC results.

  Funding Agency

Agency
National Institute of Health (NIH)
Institute
National Center for Research Resources (NCRR)
Type
Biotechnology Resource Grants (P41)
Project #
5P41RR004328-09
Application #
5224886
Study Section
Project Start
Project End
Budget Start
Budget End
Support Year
9
Fiscal Year
1996
Total Cost
Indirect Cost

  Publications

Jaganaman, Sunil; Pinto, Alex; Tarasev, Michael et al. (2007) High levels of expression of the iron-sulfur proteins phthalate dioxygenase and phthalate dioxygenase reductase in Escherichia coli. Protein Expr Purif 52:273-9
Todd, M J; Gomez, J (2001) Enzyme kinetics determined using calorimetry: a general assay for enzyme activity? Anal Biochem 296:179-87
Karantza, V; Freire, E; Moudrianakis, E N (2001) Thermodynamic studies of the core histones: stability of the octamer subunits is not altered by removal of their terminal domains. Biochemistry 40:13114-23
Griko, Y V; Remeta, D P (1999) Energetics of solvent and ligand-induced conformational changes in alpha-lactalbumin. Protein Sci 8:554-61
Chu, V; Freitag, S; Le Trong, I et al. (1998) Thermodynamic and structural consequences of flexible loop deletion by circular permutation in the streptavidin-biotin system. Protein Sci 7:848-59
Luque, I; Freire, E (1998) Structure-based prediction of binding affinities and molecular design of peptide ligands. Methods Enzymol 295:100-27
Luque, I; Gomez, J; Semo, N et al. (1998) Structure-based thermodynamic design of peptide ligands: application to peptide inhibitors of the aspartic protease endothiapepsin. Proteins 30:74-85
Gomez, J; Semo, N; Freire, E (1998) Structural thermodynamic study of the binding of renin inhibitors to endothiapepsin. Adv Exp Med Biol 436:325-8
Koder, R L; Miller, A F (1998) Overexpression, isotopic labeling, and spectral characterization of Enterobacter cloacae nitroreductase. Protein Expr Purif 13:53-60
Freire, E (1998) Statistical thermodynamic linkage between conformational and binding equilibria. Adv Protein Chem 51:255-79

Showing the most recent 10 out of 86 publications