Oct 23, 1997

DSC studies of the conformational stability of barstar wild-type

Protein Science : a Publication of the Protein Society
A SchöppeJayant B Udgaonkar

Abstract

The temperature induced unfolding of barstar wild-type of bacillus amyloliquefaciens (90 residues) has been characterized by differential scanning microcalorimetry. The process has been found to be reversible in the pH range from 6.4 to 8.3 in the absence of oxygen. It has been clearly shown by a ratio of delta HvH/delta Hcal near 1 that denaturation follows a two-state mechanism. For comparison, the C82A mutant was also studied. This mutant exhibits similar reversibility, but has a slightly lower transition temperature. The transition enthalpy of barstar wt (303 kJ mol-1) exceeds that of the C82A mutant (276 kJ mol-1) by approximately 10%. The heat capacity changes show a similar difference, delta Cp being 5.3 +/- 1 kJ mol-1 K-1 for the wild-type and 3.6 +/- 1 kJ mol-1 K-1 for the C82A mutant. The extrapolated stability parameters at 25 degrees C are delta G0 = 23.5 +/- 2 kJ mol-1 for barstar wt and delta G0 = 25.5 +/- 2 kJ mol-1 for the C82A mutant.

Mentioned in this Paper

Thermodynamics
Bacterial Proteins
Sputolysin
Bacillus amyloliquefaciens
Bacillus amyloliquefaciens ribonuclease
Alkaline Ribonuclease
Sulfhydryl Reagents
Protein Conformation
Denaturation
Calorimetry, Differential Scanning

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