D'Onofrio Mariapina, Ragona Laura, Fessas Dimitrios, Signorelli Marco, Ugolini Raffaella, Pedò Massimo, Assfalg Michael, Molinari Henriette
Dipartimento Scientifico e Tecnologico, Strada le Grazie 15, Università degli Studi di Verona, Verona, Italy.
Arch Biochem Biophys. 2009 Jan 1;481(1):21-9. doi: 10.1016/j.abb.2008.10.017. Epub 2008 Oct 21.
The folding properties of a bile acid binding protein, belonging to a subfamily of the fatty acid binding proteins, have been here investigated both by hydrogen exchange measurements, using the SOFAST NMR approach, and urea denaturation experiments. The urea unfolding profiles of individual residues, acting as single probes, were simultaneously analyzed through a global fit, according to a two-state unfolding model. The resulting conformational stability DeltaG(U)(H(2)O)=7.2+/-0.25kcal mol(-1) is in good agreement with hydrogen exchange stability DeltaG(op). While the majority of protein residues satisfy this model, few amino-acids display a singular behavior, not directly amenable to the presence of a folding intermediate, as reported for other fatty acid binding proteins. These residues are part of a protein patch characterized by enhanced plasticity. To explain this singular behavior a tentative model has been proposed which takes into account the interplay between the dynamic features and the formation of transient aggregates. A functional role for this plasticity, related to translocation across the nuclear membrane, is discussed.
本文通过使用SOFAST NMR方法进行氢交换测量以及尿素变性实验，对属于脂肪酸结合蛋白亚家族的胆汁酸结合蛋白的折叠特性进行了研究。根据两态展开模型，通过全局拟合同时分析了作为单个探针的各个残基的尿素展开曲线。所得的构象稳定性ΔG(U)(H₂O)=7.2±0.25 kcal mol⁻¹与氢交换稳定性ΔG(op)高度一致。虽然大多数蛋白质残基符合该模型，但少数氨基酸表现出奇异行为，不像其他脂肪酸结合蛋白那样直接表明存在折叠中间体。这些残基是蛋白质斑块的一部分，其特征是可塑性增强。为了解释这种奇异行为，提出了一个初步模型，该模型考虑了动态特征与瞬时聚集体形成之间的相互作用。还讨论了这种可塑性与跨核膜转运相关的功能作用。
