| Autor: |
Yang, Zhengrong W., Tendian, Susan W., Carson, W. Michael, Brouillette, Wayne J., Delucas, Lawrence J., Brouillette, Christie G. |
| Zdroj: |
Protein Science: A Publication of the Protein Society; 2004, Vol. 13 Issue 3, p830-841, 12p |
| Abstrakt: |
Dimethyl sulfoxide (DMSO) is commonly used as a cosolvent to improve the aqueous solubility of small organic compounds. Its use in a screen to identify novel inhibitors of the enzyme NAD+ synthetase led to this investigation of its potential effects on the structure and stability of this 60-kD homodimeric enzyme. Although no effects are observed on the enzyme's catalytic activity, as low as 2.5% (v/v) DMSO led to demonstrable changes in the stability of the dimer and its unfolding mechanism. In the absence of DMSO, the dimer behaves hydrodynamically as a single ideal species, as determined by equilibrium analytical ultracentrifugation, and thermally unfolds according to a two-state dissociative mechanism, based on analysis by differential scanning calorimetry (DSC). In the presence of 2.5% (v/v) DMSO, an equilibrium between the dimer and monomer is now detectable with a measured dimer association constant, Ka, equal to 5.6 × 106/M. DSC curve analysis is consistent with this finding. The data are best fit to a three-state sequential unfolding mechanism, most likely representing folded dimer ⇆ folded monomer ⇆ unfolded monomer. The unusually large change in the relative stabilities of dimer and monomer, e.g., the association equilibrium shifts from an infinitely large Ka down to ∼106/M, in the presence of relatively low cosolvent concentration is surprising in view of the significant buried surface area at the dimer interface, roughly 20% of the surface area of each monomer is buried. A hypothetical structural mechanism to explain this effect is presented. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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