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Application of the local-bulk partitioning and competitive binding models to interpret preferential interactions of glycine betaine and urea with protein surface.
Biochemistry. 2004 Jul 20; 43(28):9276-88.B

Abstract

Two thermodynamic models have been developed to interpret the preferential accumulation or exclusion of solutes in the vicinity of biopolymer surface and the effects of these solutes on protein processes. The local-bulk partitioning model treats solute (and water) as partitioning between the region at/or near the protein surface (the local domain) and the bulk solution. The solvent exchange model analyzes a 1:1 competition between water and solute molecules for independent surface sites. Here we apply each of these models to interpret thermodynamic data for the interactions of urea and the osmoprotectant glycine betaine (N,N,N-trimethylglycine; GB) with the surface exposed in unfolding the marginally stable lacI HTH DNA binding domain. The partition coefficient K(P) quantifying accumulation of urea at this protein surface (K(P) approximately equal 1.1) is only weakly dependent on urea concentration up to 6 M urea. However, K(P) quantifying exclusion of GB from the vicinity of this protein surface increases from 0.83 (extrapolated to 0 M GB) to 1.0 (indicating that local and bulk GB concentrations are equal) at 4 M GB (activity > 40 M). We interpret the significant concentration dependence of K(P) for GB, predicted to be general for excluded, nonideal solutes such as GB, as a modest (8%) attenuation of the GB concentration dependence of solute nonideality in the local domain relative to that in the bulk solution. Above 4 M, K(P) for the interaction of GB with the surface exposed in protein unfolding is predicted to exceed unity, which explains the maximum in thermal stability observed for RNase and lysozyme at 4 M GB (Santoro, M. M., Liu, Y. F., Khan, S. M. A., Hou, L. X., and Bolen, D. W. (1992) Biochemistry 31, 5278-5283). Both thermodynamic models provide good two-parameter fits to GB and urea data for lacI HTH unfolding over a wide concentration range. The solute partitioning model allows for a full spectrum of attenuation effects in the local domain, encompasses the cases treated by the competitive binding model, and provides a somewhat better two-parameter fit of effects of high GB concentration on lacI HTH stability. Parameters of this fit should be applicable to isothermal and thermal unfolding data for all proteins with similar compositions of surface exposed in unfolding.

Authors+Show Affiliations

Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.No affiliation info available

Pub Type(s)

Journal Article
Research Support, U.S. Gov't, Non-P.H.S.
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

15248785

Citation

Felitsky, Daniel J., and M Thomas Record. "Application of the Local-bulk Partitioning and Competitive Binding Models to Interpret Preferential Interactions of Glycine Betaine and Urea With Protein Surface." Biochemistry, vol. 43, no. 28, 2004, pp. 9276-88.
Felitsky DJ, Record MT. Application of the local-bulk partitioning and competitive binding models to interpret preferential interactions of glycine betaine and urea with protein surface. Biochemistry. 2004;43(28):9276-88.
Felitsky, D. J., & Record, M. T. (2004). Application of the local-bulk partitioning and competitive binding models to interpret preferential interactions of glycine betaine and urea with protein surface. Biochemistry, 43(28), 9276-88.
Felitsky DJ, Record MT. Application of the Local-bulk Partitioning and Competitive Binding Models to Interpret Preferential Interactions of Glycine Betaine and Urea With Protein Surface. Biochemistry. 2004 Jul 20;43(28):9276-88. PubMed PMID: 15248785.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Application of the local-bulk partitioning and competitive binding models to interpret preferential interactions of glycine betaine and urea with protein surface. AU - Felitsky,Daniel J, AU - Record,M Thomas,Jr PY - 2004/7/14/pubmed PY - 2004/9/10/medline PY - 2004/7/14/entrez SP - 9276 EP - 88 JF - Biochemistry JO - Biochemistry VL - 43 IS - 28 N2 - Two thermodynamic models have been developed to interpret the preferential accumulation or exclusion of solutes in the vicinity of biopolymer surface and the effects of these solutes on protein processes. The local-bulk partitioning model treats solute (and water) as partitioning between the region at/or near the protein surface (the local domain) and the bulk solution. The solvent exchange model analyzes a 1:1 competition between water and solute molecules for independent surface sites. Here we apply each of these models to interpret thermodynamic data for the interactions of urea and the osmoprotectant glycine betaine (N,N,N-trimethylglycine; GB) with the surface exposed in unfolding the marginally stable lacI HTH DNA binding domain. The partition coefficient K(P) quantifying accumulation of urea at this protein surface (K(P) approximately equal 1.1) is only weakly dependent on urea concentration up to 6 M urea. However, K(P) quantifying exclusion of GB from the vicinity of this protein surface increases from 0.83 (extrapolated to 0 M GB) to 1.0 (indicating that local and bulk GB concentrations are equal) at 4 M GB (activity > 40 M). We interpret the significant concentration dependence of K(P) for GB, predicted to be general for excluded, nonideal solutes such as GB, as a modest (8%) attenuation of the GB concentration dependence of solute nonideality in the local domain relative to that in the bulk solution. Above 4 M, K(P) for the interaction of GB with the surface exposed in protein unfolding is predicted to exceed unity, which explains the maximum in thermal stability observed for RNase and lysozyme at 4 M GB (Santoro, M. M., Liu, Y. F., Khan, S. M. A., Hou, L. X., and Bolen, D. W. (1992) Biochemistry 31, 5278-5283). Both thermodynamic models provide good two-parameter fits to GB and urea data for lacI HTH unfolding over a wide concentration range. The solute partitioning model allows for a full spectrum of attenuation effects in the local domain, encompasses the cases treated by the competitive binding model, and provides a somewhat better two-parameter fit of effects of high GB concentration on lacI HTH stability. Parameters of this fit should be applicable to isothermal and thermal unfolding data for all proteins with similar compositions of surface exposed in unfolding. SN - 0006-2960 UR - https://www.unboundmedicine.com/medline/citation/15248785/Application_of_the_local_bulk_partitioning_and_competitive_binding_models_to_interpret_preferential_interactions_of_glycine_betaine_and_urea_with_protein_surface_ L2 - https://doi.org/10.1021/bi049862t DB - PRIME DP - Unbound Medicine ER -