Rocco Alessandro Guerini, Mollica Luca, Ricchiuto Piero, Baptista António M, Gianazza Elisabetta, Eberini Ivano
Gruppo di Studio per la Proteomica e la Struttura delle Proteine, Dipartimento di Scienze Farmacologiche, Università degli Studi di Milano, Milano, Italy.
Biophys J. 2008 Mar 15;94(6):2241-51. doi: 10.1529/biophysj.107.115535. Epub 2007 Dec 7.
Correct folding is critical for the biological activities of proteins. As a contribution to a better understanding of the protein (un)folding problem, we studied the effect of temperature and of urea on peptostreptococcal Protein L destructuration. We performed standard molecular dynamics simulations at 300 K, 350 K, 400 K, and 480 K, both in 10 M urea and in water. Protein L followed at least two alternative unfolding pathways. Urea caused the loss of secondary structure acting preferentially on the beta-sheets, while leaving the alpha-helices almost intact; on the contrary, high temperature preserved the beta-sheets and led to a complete loss of the alpha-helices. These data suggest that urea and high temperature act through different unfolding mechanisms, and protein secondary motives reveal a differential sensitivity to various denaturant treatments. As further validation of our results, replica-exchange molecular dynamics simulations of the temperature-induced unfolding process in the presence of urea were performed. This set of simulations allowed us to compute the thermodynamical parameters of the process and confirmed that, in the configurational space of Protein L unfolding, both of the above pathways are accessible, although to a different relative extent.
正确折叠对于蛋白质的生物学活性至关重要。为了更好地理解蛋白质（去）折叠问题，我们研究了温度和尿素对消化链球菌蛋白L结构破坏的影响。我们在10 M尿素溶液和水中分别于300 K、350 K、400 K和480 K进行了标准分子动力学模拟。蛋白L至少遵循两条不同的解折叠途径。尿素导致二级结构丧失，优先作用于β折叠，而α螺旋几乎保持完整；相反，高温保留了β折叠并导致α螺旋完全丧失。这些数据表明，尿素和高温通过不同的解折叠机制起作用，并且蛋白质二级结构基序对各种变性处理表现出不同的敏感性。作为对我们结果的进一步验证，我们在有尿素存在的情况下对温度诱导的解折叠过程进行了副本交换分子动力学模拟。这组模拟使我们能够计算该过程的热力学参数，并证实，在蛋白L解折叠的构型空间中，上述两条途径均可行，尽管相对程度不同。
