重复蛋白机械展开的理论模型。
A theoretical model for the mechanical unfolding of repeat proteins.
作者信息
Makarov Dmitrii E
机构信息
Department of Chemistry and Biochemistry and Institute for Theoretical Chemistry, University of Texas at Austin, Austin, Texas, USA.
出版信息
Biophys J. 2009 Mar 18;96(6):2160-7. doi: 10.1016/j.bpj.2008.12.3899.
We consider the mechanical stretching of a polypeptide chain formed by multiple interacting repeats. The folding thermodynamics and the interactions among the repeats are described by the Ising model. Unfolded repeats act as soft entropic springs, whereas folded repeats respond to a force as stiffer springs. We show that the resulting force-extension curve may exhibit a pronounced force maximum corresponding to the unfolding of the first repeat. This event is followed by the unfolding of the remaining repeats, which takes place at a lower force. As the protein extension is increased, the force-extension curve of a sufficiently long repeat protein displays a plateau, where the force remains nearly constant and the protein unfolds sequentially so that the number of unfolded repeats is proportional to the extension. Such a sequential mechanical unfolding mechanism is displayed even by the repeat proteins whose thermal denaturation is highly cooperative, provided that they are long enough. By contrast, the unfolding of short repeat progressions can be cooperative.
我们考虑由多个相互作用的重复序列形成的多肽链的机械拉伸。折叠热力学和重复序列之间的相互作用由伊辛模型描述。未折叠的重复序列充当柔软的熵弹簧，而折叠的重复序列对力的响应则像更硬的弹簧。我们表明，由此产生的力-伸长曲线可能会出现一个明显的力最大值，对应于第一个重复序列的展开。此事件之后是其余重复序列的展开，这发生在较低的力下。随着蛋白质伸长的增加，足够长的重复序列蛋白质的力-伸长曲线会显示出一个平台期，在此期间力几乎保持恒定，并且蛋白质依次展开，使得未折叠重复序列的数量与伸长成正比。即使是热变性高度协同的重复序列蛋白质，只要它们足够长，也会表现出这种顺序性机械展开机制。相比之下，短重复序列的展开可能是协同的。
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