Interleukin-1 Folding between pH 5 and 7: Experimental Evidence for Three-State Folding Behavior and Robust Transitio
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- 作者：John M. Finke and Patricia A. Jennings
- 刊名：Biochemistry
- 出版年：2002
- 出版时间：December 17, 2002
- 年：2002
- 卷：41
- 期：50
- 页码：15056 - 15067
- 全文大小：290K
- 年卷期：v.41,no.50(December 17, 2002)
- ISSN：1520-4995
文摘
The thermodynamic stability and folding kinetics of the all 
-sheet protein interleukin-1were measured between 0 and 4 M GdmCl concentrations and pH 5-7. Native interleukin-1 undergoesa 3.5 kcal/mol decrease in thermodynamic stability, 
, as pH is increased from 5 to 7. The nativestate parameter mNU, measuring protein destabilization/[GdmCl], remains constant between pH 5 and 7,indicating that the solvent-exposed surface area difference between the native state and unfolded ensembleis unchanged across this pH range. Similarly, pH changes between 5 and 7 decrease only the thermodynamicstability, GH2O, and not the m-values, of the kinetic intermediate and transition states. This finding isshown to be consistent with transition state configurations which continue to be the high-energyconfigurations of the transition state in the face of changing stability conditions. A three-state foldingmechanism U 
I N is shown to be sufficient in characterizing IL-1 folding under all conditionsstudied. The m-values of refolding transitions are much larger than the m-values of unfolding transitions,indicating that that the fast, T2 (U I), and slow, T1 (I N), transition states are highly similar to theintermediate I and native state N, respectively. Many of the folding properties of interleukin-1 are sharedamong other members of the -trefoil protein family, although clear differences can exist.
-sheet protein interleukin-1were measured between 0 and 4 M GdmCl concentrations and pH 5-7. Native interleukin-1 undergoesa 3.5 kcal/mol decrease in thermodynamic stability, , as pH is increased from 5 to 7. The nativestate parameter mNU, measuring protein destabilization/[GdmCl], remains constant between pH 5 and 7,indicating that the solvent-exposed surface area difference between the native state and unfolded ensembleis unchanged across this pH range. Similarly, pH changes between 5 and 7 decrease only the thermodynamicstability, GH2O, and not the m-values, of the kinetic intermediate and transition states. This finding isshown to be consistent with transition state configurations which continue to be the high-energyconfigurations of the transition state in the face of changing stability conditions. A three-state foldingmechanism U I N is shown to be sufficient in characterizing IL-1 folding under all conditionsstudied. The m-values of refolding transitions are much larger than the m-values of unfolding transitions,indicating that that the fast, T2 (U I), and slow, T1 (I N), transition states are highly similar to theintermediate I and native state N, respectively. Many of the folding properties of interleukin-1 are sharedamong other members of the -trefoil protein family, although clear differences can exist.