Preferential interactions of urea with lysozyme and their linkage to protein denaturation
Preferential interactions of urea with lysozyme and their linkage to protein denaturation
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DOI：
10.1016/s0301-4622(03)00106-6
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发表时间：
2003-09-01
影响因子：
3.8
通讯作者：
Xie, GF
中科院分区：
文献类型：
--
作者：
Timasheff, SN;Xie, GF
在尿素的存在下，在溶菌酶的变性所涉及的相互作用进行了检查，通过热转换研究和测量的优先相互作用的尿素与蛋白质在pH 7.0，在那里它仍然是本地高达9.3 M尿素，并在pH 2.0，在那里它经历了2.5和5.0 M尿素之间的过渡。尿素对溶菌酶的去稳定作用与尿素的摩尔浓度呈线性关系，Δ G（u）（o）= Δ G（w）（o）-2. 1 M-u，其中Δ G（u）（o）和Δ G（w）（o）分别为尿素和水的不可逆arrowD反应的标准自由能变化。结合测量的优先结合给出了优先结合的增量Δ Gamma（23）=Gamma（23）（D）-Gamma（23）（N）在M-u中也是线性的结果。温度依赖性研究的优先相互作用允许的转让焓，Δ（H）的bar（o）（2，tr），和熵，Δ（S）的bar（o）（2，tr）的溶菌酶从水到尿素在天然和变性状态的评估。发现这些值与脲间氢键形成的焓和熵一致（Schellman，1955; Kauzmann，1959），估计的Delta（H）/bar（o）（2，tr）=ca。-2.5 kcal mol（-1）和δ（S）/bar（o）（2，tr）=ca。-7.0 e.u.每个站点。结果分析得出结论，变性形式的稳定主要是通过优先结合新暴露的肽基团。结合稳定渗压剂通过优先排除肽基团而起作用的知识（Liu和Bolen，1995），得出了一般结论，即共溶剂对蛋白质的稳定和去稳定主要通过与变性时新暴露的肽基团的优先相互作用来控制。(C)2003 Elsevier Science B. V.保留所有权利。
The interactions involved in the denaturation of lysozyme in the presence of urea were examined by thermal transition studies and measurements of preferential interactions of urea with the protein at pH 7.0, where it remains native up to 9.3 M urea, and at pH 2.0, where it undergoes a transition between 2.5 and 5.0 M urea. The destabilization of lysozyme by urea was found to follow the linear dependence on urea molar concentration, M-u, DeltaG(u)(o)=DeltaG(w)(o)-2.1 M-u, over the combined data, where DeltaG(u)(o) and DeltaG(w)(o) are the standard free energy changes of the Nreversible arrowD reaction in urea and water, respectively. Combination with the measured preferential binding gave the result that the increment of preferential binding, deltaGamma(23)=Gamma(23)(D)-Gamma(23)(N), is also linear in M-u. A temperature dependence study of preferential interactions permitted the evaluation of the transfer enthalpy, Delta(H) over bar (o)(2,tr), and entropy, Delta(S) over bar (o)(2,tr) of lysozyme from water into urea in both the native and denatured states. These values were found to be consistent with the enthalpy and entropy of formation of inter urea hydrogen bonds (Schellman, 1955; Kauzmann, 1959), with estimated values of Delta(H) over bar (o)(2,tr)=ca. -2.5 kcal mol(-1) and Delta(S) over bar (o)(2,tr)=ca. -7.0 e.u. per site. Analysis of the results led to the conclusion that the stabilization of the denatured form was predominantly by preferential binding to newly exposed peptide groups. Combination with the knowledge that stabilizing osmolytes act by preferential exclusion from peptide groups (Liu and Bolen, 1995) has led to the general conclusion that both the stabilization and destabilization of proteins by co-solvents are controlled predominantly by preferential interactions with peptide groups newly exposed on denaturation. (C) 2003 Elsevier Science B.V. All rights reserved.