How are proteins mechanically unfolded? A study spanning fundamental principles and biological complexity

蛋白质如何机械展开？

• 批准号: BB/D017173/1
• 负责人: David Brockwell
• 金额: $ 37.05万
• 依托单位: University of Leeds
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2006
• 资助国家: 英国
• 起止时间: 2006 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=BB%2FD017173%2F1
• 关键词: How; proteins; mechanically; unfolded; study

To be functional most proteins need to fold up into a well defined three dimensional structure. The probability that a protein remains in this state over a period of time is related to its thermodynamic stability: the greater the stability, the greater the proportion of folded active proteins. Proteins have many different functions in cells including energy generation, locomotion and structural roles. Mechanical force, which can denature proteins, is applied onto these proteins during many of these activities and, to maintain their function, proteins have to be mechanically resistant. Using techniques that allow the manipulation of single protein molecules, it is now possible to measure the mechanical strength of proteins in the laboratory. This technique uses an instrument called the atomic force microscope (AFM). However, the mechanical stability of proteins has been found to be unrelated to a protein's thermodynamic stability but correlates well with how the different types of a protein's sub-structure are arranged in each protein. The reason for this is unclear but it is thought that regions in proteins that are bound less tightly to the rest of the structure may be more likely to unfold when force is applied onto this part of the protein. As a consequence, the force at which a protein unfolds depends upon the points at which the force is exerted onto the protein. It has recently been discovered that cells possess large cylindrical protein complexes that are able to unfold and digest proteins which have been tagged for destruction in order to control cellular processes. It is thought that these 'unfoldases' (ClpXP for example) unfold even very stable proteins by applying force onto the proteins to be degraded. The rate at which proteins are unfolded by the Clp system appears to correlate with the stability of the protein local to the position of the degradation tag - an observation similar to that reported for the unfolding process measured by the AFM. The underlying mechanism for either process is, at present, unknown. This project aims to probe the fundamental origins of the mechanical properties of proteins by measuring how the presence of regions of local instability in proteins correlates with the mechanical strength of proteins when denatured using the AFM and when degraded by the cellular unfoldase ClpXP.

要成为功能性的大多数蛋白质都需要折叠成一个定义明确的三维结构。蛋白在一段时间内保持在该状态的可能性与其热力学稳定性有关：稳定性越大，折叠活性蛋白的比例就越大。蛋白质在细胞中具有许多不同的功能，包括能量产生，运动和结构作用。在许多这些活性过程中，机械力可以将蛋白质的蛋白质施加到这些蛋白质上，并且为了维持其功能，蛋白质必须在机械上具有抗性。使用允许操纵单蛋白分子的技术，现在可以测量实验室中蛋白质的机械强度。该技术使用一种称为原子力显微镜（AFM）的仪器。然而，已经发现蛋白质的机械稳定性与蛋白质的热力学稳定性无关，但与在每种蛋白质中排列的不同类型的蛋白质亚结构的排列方式很好地相关。造成这种情况的原因尚不清楚，但人们认为，与结构的其余部分紧密结合的蛋白质区域可能更可能在将力施加到蛋白质的这一部分时展开。结果，蛋白质展开的力取决于将力施加到蛋白质上的点。最近已经发现，细胞具有能够展开的大圆柱蛋白复合物，并消化已被标记为破坏以控制细胞过程的蛋白质。人们认为，这些“展开酶”（例如CLPXP）通过将力施加到要降解的蛋白质上，即使蛋白质也非常稳定。 CLP系统展开蛋白质的速率似乎与蛋白质局部与降解标签的位置的稳定性相关 - 这是AFM测量的展开过程所报道的观察值。目前，这两种过程的基本机制是未知的。该项目的目的是通过测量使用AFM变性并被细胞Infloctal from from fromoldase clpxp降解时，旨在通过测量蛋白质中局部不稳定性区域的存在与蛋白质强度相关的蛋白质机械性能的基本起源。

项目成果

Identification of a mechanical rheostat in the hydrophobic core of protein L.

• DOI: 10.1016/j.jmb.2009.08.015
• 发表时间: 2009-10-16
• 期刊: JOURNAL OF MOLECULAR BIOLOGY
• 影响因子: 5.6
• 作者: Sadler, David P.;Petrik, Eva;Taniguchi, Yukinori;Pullen, James R.;Kawakami, Masaru;Radford, Sheena E.;Brockwell, David J.
• 通讯作者: Brockwell, David J.