School of Chemistry, National University of Ireland Galway, Galway, Ireland.
J Chem Phys. 2017 Nov 21;147(19):195101. doi: 10.1063/1.4994561.
As proteins contain both hydrophobic and hydrophilic amino acids, they will readily adsorb onto interfaces between water and hydrophobic fluids such as oil. This adsorption normally causes changes in the protein structure, which can result in loss of protein function and irreversible adsorption, leading to the formation of protein interfacial films. While this can be advantageous in some applications (e.g., food technology), in most cases it limits our ability to exploit protein functionality at interfaces. To understand and control protein interfacial adsorption and function, it is necessary to understand the microscopic conformation of proteins at liquid interfaces. In this paper, molecular dynamics simulations are used to investigate the adsorption and conformation of two similar proteins, lysozyme and α-lactalbumin, at a water-octane interface. While they both adsorb onto the interface, α-lactalbumin does so in a specific orientation, mediated by two amphipathic helices, while lysozyme adsorbs in a non-specific manner. Using replica exchange simulations, both proteins are found to possess a number of distinct interfacial conformations, with compact states similar to the solution conformation being most common for both proteins. Decomposing the different contributions to the protein energy at oil-water interfaces suggests that conformational change for α-lactalbumin, unlike lysozyme, is driven by favourable protein-oil interactions. Revealing these differences between the factors that govern the conformational change at interfaces in otherwise similar proteins can give insight into the control of protein interfacial adsorption, aggregation, and function.
由于蛋白质既含有疏水氨基酸又含有亲水氨基酸，因此它们会轻易地吸附在水和疏油液体（如油）之间的界面上。这种吸附通常会导致蛋白质结构发生变化，从而导致蛋白质功能丧失和不可逆吸附，形成蛋白质界面膜。虽然这在某些应用中可能是有利的（例如食品技术），但在大多数情况下，它限制了我们在界面处利用蛋白质功能的能力。为了理解和控制蛋白质界面吸附和功能，有必要了解蛋白质在液体界面处的微观构象。在本文中，使用分子动力学模拟研究了两种相似蛋白质溶菌酶和α-乳白蛋白在水-辛烷界面上的吸附和构象。虽然它们都吸附在界面上，但α-乳白蛋白通过两个两亲性螺旋以特定的取向吸附，而溶菌酶则以非特异性的方式吸附。使用复制交换模拟，发现两种蛋白质都具有许多不同的界面构象，与溶液构象相似的紧凑状态对两种蛋白质都最常见。分解蛋白质在油水界面上的能量的不同贡献表明，与溶菌酶不同，α-乳白蛋白的构象变化是由有利的蛋白质-油相互作用驱动的。揭示这些相似蛋白质界面构象变化的控制因素之间的差异，可以深入了解蛋白质界面吸附、聚集和功能的控制。
