点突变对胱抑素结构及淀粉样聚集特性影响的分子动力学研究
发布时间：2018-08-27 15:26
【摘要】：胱抑素的淀粉样突变体在人体内发生淀粉样聚集后，会引起脑淀粉样血管病和阿尔茨海默病。其聚集的分子机制与胱抑素单体通过结构域交换形成稳定的二聚体密切相关。但是，迄今为止，有关胱抑素淀粉样突变体的单体如何通过构象转换形成二聚体的机制一直缺乏足够的实验论证。 本研究基于前期的生化和细胞水平的研究成果，利用分子动力学模拟的方法，研究点突变对胱抑素结构及淀粉样聚集特性的影响。对突变体I66Q的模拟结果表明，与野生型胱抑素相比，其构象发生显著变化，稳定性明显降低。其中AS、loop区域以及α-β界面的变化最明显，其结构更加灵活。这些变化使得胱抑素整体结构变得松散，AS区域与β区域的张口变大，处于伸展状态，作用力减弱，因此更易诱导参与结构域交换的两个亚结构域分开。对I66Q/I108T的模拟结果表明，I108T对I66Q起着促进作用，其中AS、loop、helix1变化更加明显，结构中疏水核心面积增大，整体结构疏散，AS区域的helix2基本全部解螺旋为coil结构，AS区域和β区域的张口几乎全部打开，相互作用力严重减弱，极易发生结构域交换。随后的研究发现，Val55位点突变V55D、V55N对I66Q突变体都有一定的稳定作用，但V55N突变体的稳定作用更为显著。这种稳定作用的分子机制主要表现在V55D、V55N点突变增强了cC的55位残基的稳定性，从而进一步稳定了Loop1、β2-β3以及α2-helix。而55位残基稳定性的不同是由不同突变体形成的氢键数量来决定的，其中55位残基与Gln53形成的氢键可能发挥着最重要的作用。另外我们也发现，V55D、V55N两种突变体对I66Q疏水核心都有显著的稳定作用，并伴随着疏水核心氢键的轻微增加，进而增强了I66Q单体的稳定性。 上述研究结果不仅有助于在理论上解释点突变影响cC单体稳定性和分子间聚集的分子机制，，对于深入研究胱抑素结构域交换的分子机制也具有重要的促进意义。另外，本研究中所采用的研究方法，为其它蛋白质错误折叠引起的蛋白质淀粉样聚集疾病的分子机制研究提供了一个新的思路。
[Abstract]:Amyloid mutants of cystatin cause cerebral amyloid angiopathy and Alzheimer's disease after amyloid aggregation occurs in the human body. The molecular mechanism of its aggregation is closely related to the exchange of cystatin monomers through domain to form stable dimers. However, the mechanism of conformational conversion of cystatin amyloid mutant monomers to dimer has not been sufficiently demonstrated. In this study, the effects of point mutation on cystatin structure and amyloid aggregation were studied by molecular dynamics simulation based on previous biochemical and cellular studies. The simulation results of the mutant I66Q showed that the conformation and stability of the mutant I66Q were significantly different from those of wild type cystatin. The change of AS,loop region and 伪-尾 interface is the most obvious, and its structure is more flexible. These changes make the whole structure of cystatin become loose, the opening of as region and 尾 region becomes larger, and the interaction force is weakened, so it is easier to induce the separation of two subdomains involved in domain exchange. The simulation results of I66Q/I108T show that I108T promotes I66Q, and the change of AS,loop,helix1 is more obvious, and the hydrophobic core area in the structure increases. The helix2 unspirals in the as region of the whole structure are almost completely opened in the as and 尾 region of the coil structure, and the interaction forces are weakened seriously, so the domain exchange is easy to occur. Subsequently, it was found that the V55D- V55N mutation had a certain stabilizing effect on the I66Q mutants, but the V55N mutants had a more significant stabilizing effect on the I66Q mutants. The molecular mechanism of this stabilization is that the point mutation of V55DV 55N enhances the stability of 55 residues of cC, thus further stabilizing Loop1, 尾 2- 尾 3 and 伪 2-helix. The stability of 55 residues is determined by the number of hydrogen bonds formed by different mutants, and the hydrogen bonds formed between 55 residues and Gln53 may play the most important role. These results not only help to explain the molecular mechanism of point mutation affecting the stability and intermolecular aggregation of cC monomers, but also contribute to the further study of the molecular mechanism of cystatin domain exchange. In addition, the methods used in this study provide a new idea for the study of molecular mechanism of protein amyloid aggregation disease caused by other protein misfolding.
【学位授予单位】：辽宁大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：R341
本文编号：2207690
[Abstract]:Amyloid mutants of cystatin cause cerebral amyloid angiopathy and Alzheimer's disease after amyloid aggregation occurs in the human body. The molecular mechanism of its aggregation is closely related to the exchange of cystatin monomers through domain to form stable dimers. However, the mechanism of conformational conversion of cystatin amyloid mutant monomers to dimer has not been sufficiently demonstrated. In this study, the effects of point mutation on cystatin structure and amyloid aggregation were studied by molecular dynamics simulation based on previous biochemical and cellular studies. The simulation results of the mutant I66Q showed that the conformation and stability of the mutant I66Q were significantly different from those of wild type cystatin. The change of AS,loop region and 伪-尾 interface is the most obvious, and its structure is more flexible. These changes make the whole structure of cystatin become loose, the opening of as region and 尾 region becomes larger, and the interaction force is weakened, so it is easier to induce the separation of two subdomains involved in domain exchange. The simulation results of I66Q/I108T show that I108T promotes I66Q, and the change of AS,loop,helix1 is more obvious, and the hydrophobic core area in the structure increases. The helix2 unspirals in the as region of the whole structure are almost completely opened in the as and 尾 region of the coil structure, and the interaction forces are weakened seriously, so the domain exchange is easy to occur. Subsequently, it was found that the V55D- V55N mutation had a certain stabilizing effect on the I66Q mutants, but the V55N mutants had a more significant stabilizing effect on the I66Q mutants. The molecular mechanism of this stabilization is that the point mutation of V55DV 55N enhances the stability of 55 residues of cC, thus further stabilizing Loop1, 尾 2- 尾 3 and 伪 2-helix. The stability of 55 residues is determined by the number of hydrogen bonds formed by different mutants, and the hydrogen bonds formed between 55 residues and Gln53 may play the most important role. These results not only help to explain the molecular mechanism of point mutation affecting the stability and intermolecular aggregation of cC monomers, but also contribute to the further study of the molecular mechanism of cystatin domain exchange. In addition, the methods used in this study provide a new idea for the study of molecular mechanism of protein amyloid aggregation disease caused by other protein misfolding.
【学位授予单位】：辽宁大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：R341
【参考文献】
相关期刊论文 前1条
1 宋有涛;张慧丽;宫雅楠;;淀粉样蛋白沉积疾病在细胞水平的研究进展[J];细胞生物学杂志;2008年05期
本文编号：2207690
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