Cold- and pressure-induced dissociation of protein aggregates and amyloid fibrils
Cold- and pressure-induced dissociation of protein aggregates and amyloid fibrils
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DOI：
10.1002/anie.200802027
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发表时间：
2008-01-01
影响因子：
16.6
通讯作者：
Winter, Roland
中科院分区：
文献类型：
--
作者：
Mishra, Rajesh;Winter, Roland
蛋白质折叠是蛋白质生命中最重要的步骤之一。如果在获得天然构象时发生一些故障，这将使多肽完全失活，或者甚至更糟，它可以产生错误折叠的分子，该分子可以干扰或阻断细胞机器的组分，达到导致细胞故障甚至死亡的程度。近年来，很明显，许多人类疾病都与折叠过程中的畸变有关。[1，2]这些疾病也被称为“蛋白质构象疾病”，包括阿尔茨海默病（责任蛋白：Aβ）、帕金森病（α突触核蛋白）、朊病毒蛋白相关脑病和II型糖尿病（胰岛淀粉样多肽，IAPP）。淀粉样沉积物表现出类似的纤维状亚显微结构。所有淀粉样蛋白在二级结构中是有序的，包括核心交叉β-折叠结构，其中连续的β折叠与垂直于原纤维轴的β链形成。[1]已经表明，一般的淀粉样蛋白构象，交叉β结构，可能是聚集蛋白的普遍能量最小值。典型地，淀粉样蛋白原纤维由2至6个未分支的原丝（2-5 nm宽）组成，所述原丝横向缔合或扭曲在一起以形成4-13 nm宽的原纤维。一旦形成，淀粉样蛋白的刚性结构和获得的深层能量最小值使这些结构非常稳定，难以溶解。[3]这些聚集体结构的形成所涉及的分子机制仍然知之甚少，这是由于这些不溶性结构非常大（就摩尔质量而言）并且通常不能结晶的事实。虽然已知淀粉样蛋白结构是有毒的，但关于其在疾病中的作用有相当多的讨论。还表明前原纤维聚集体比淀粉样原纤维本身毒性更大。[1，4]在探索淀粉样蛋白原纤维的稳定性和能量学的努力中，压力和温度扰动以及共溶剂依赖性一直是最近研究的焦点。自从1914年诺贝尔奖获得者PW Bridgman发现高压诱导的蛋白质解折叠和变性以来，在许多研究中已经表明静水压可能导致维持天然蛋白质结构的分子间相互作用的破坏，这伴随着蛋白质-水系统体积的减少和同时的解折叠。[5-9]随后，高静水压（HHP）也已被证明是有效的解聚和蛋白质从体外制备的不溶性聚集体的重折叠。[10]表达蛋白质热力学稳定性的合适方法是将能量景观作为温度、压力和溶液条件的多维函数。当溶液条件（pH值、离子强度、盐和共溶剂浓度）保持恒定时，蛋白质的稳定性仅是温度和压力的函数。相对于某个参考点T0，p0（例如，环境压力下的解折叠温度），变性（解折叠）和天然状态之间的吉布斯自由能差ΔuG（T，p）可以近似计算-假设ΔuG（T，p）的二阶泰勒级数在T0，p0附近相对于T和p展开-如等式（1）所示。[第十一届]
Protein folding is one of the most crucial steps during the life of a protein. If some malfunction occurs in achieving the native conformation, this will render the polypeptide totally inactive, or even worse, it can produce a misfolded molecule that can interfere with or block components of the cellular machinery to the point of causing cell malfunction or even death. In recent years, it has become evident that a wide range of human diseases are associated with aberrations in the folding process.[1, 2] These diseases, which are also called “protein conformational diseases”, include Alzheimer s disease (responsible protein: Aβ), Parkinson s disease (αsynuclein), prion protein related encephalopathies, and type II diabetes mellitus (islet amyloid polypeptide, IAPP). Amyloid deposits exhibit similar, fibrillar submicroscopic structures. All amyloid is ordered in secondary structures, including a core cross β-sheet structure, in which continuous β sheets are formed with β strands running perpendicular to the fibril axis.[1] It has been suggested that the generic amyloid conformation, the cross β structure, may be a universal energetic minimum for aggregated proteins. Typically, amyloid fibrils consist of two to six unbranched protofilaments (2–5 nm wide) associated laterally or twisted together to form fibrils that are 4–13 nm wide. Once formed, the rigid structure of amyloids and the deep energy minima acquired make those structures extremely stable and hard to solubilize.[3] The molecular mechanisms involved in the formation of these aggregate structures are still poorly understood, which is due to the fact that these insoluble structures are very large (in terms of molar mass) and generally cannot be crystallized. Although the amyloid structure is known to be toxic, there is considerable discussion as to its role in disease. It has also been suggested that the prefibrillar aggregates are more toxic than the amyloid fibrils themselves.[1, 4] In efforts to probe the stability and energetics of amyloid fibril, pressure and temperature perturbation as well as cosolvent dependence have been the focus of recent studies.Since the discovery of high-pressure-induced protein unfolding and denaturation by Nobel laureate PW Bridgman in 1914, it has been shown in numerous studies that hydrostatic pressure may lead to disruption of the intermolecular interactions maintaining the native protein structure, which is accompanied by a decrease in volume of the protein–water system and simultaneous unfolding.[5–9] Subsequently, high hydrostatic pressures (HHP) have also been shown to be effective for disaggregation and refolding of proteins from insoluble aggregates prepared in vitro.[10] The appropriate way of expressing the thermodynamic stability of a protein is an energy landscape as a multidimensional function of temperature, pressure, and solution conditions. When the solution conditions (pH value, ionic strength, salt and cosolvent concentration) are kept constant, the stability of the protein is a function of only temperature and pressure. The Gibbs free energy difference ΔuG (T, p) between the denatured (unfolded) and native state, relative to some reference point T0, p0 (eg, the unfolding temperature at ambient pressure), can be approximated—assuming a secondorder Taylor series of ΔuG (T, p) expanded with respect to T and p around T0, p0—as given in Equation (1).[11]