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终点靶向分子动力学:钾通道中的大规模构象变化

End-point targeted molecular dynamics: large-scale conformational changes in potassium channels.

作者信息

Mashl R J, Jakobsson E

机构信息

National Center for Supercomputing Applications, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.

出版信息

Biophys J. 2008 Jun;94(11):4307-19. doi: 10.1529/biophysj.107.118778. Epub 2008 Feb 29.

Abstract

Large-scale conformational changes in proteins that happen often on biological time scales may be relatively rare events on the molecular dynamics time scale. We have implemented an approach to targeted molecular dynamics called end-point targeted molecular dynamics that transforms proteins between two specified conformational states through the use of nonharmonic "soft" restraints. A key feature of the method is that the protein is free to discover its own conformational pathway through the plethora of possible intermediate states. The method is applied to the Shaker K(v)1.2 potassium channel in implicit solvent. The rate of cycling between the open and closed states was varied to explore how slow the cycling rate needed to be to ensure that microscopic reversibility along the transition pathways was well approximated. Results specific to the K(+) channel include: 1), a variation in backbone torsion angles of residues near the Pro-Val-Pro motif in the inner helix during both opening and closing; 2), the identification of possible occlusion sites in the closed channel located among Pro-Val-Pro residues and downstream; 3), a difference in the opening and closing pathways of the channel; and 4), evidence of a transient intermediate structural substate. The results also show that likely intermediate conformations during the opening-closing process can be generated in computationally tractable simulation times.

摘要

蛋白质中经常在生物学时间尺度上发生的大规模构象变化,在分子动力学时间尺度上可能是相对罕见的事件。我们实现了一种称为端点靶向分子动力学的靶向分子动力学方法,该方法通过使用非谐“软”约束在两个指定的构象状态之间转换蛋白质。该方法的一个关键特征是蛋白质可以自由地通过大量可能的中间状态发现其自身的构象途径。该方法应用于隐式溶剂中的Shaker K(v)1.2钾通道。改变开放态和关闭态之间的循环速率,以探索循环速率需要多慢才能确保沿过渡途径的微观可逆性得到很好的近似。钾通道特有的结果包括:1),在内螺旋中靠近Pro-Val-Pro基序的残基的主链扭转角在开放和关闭过程中均发生变化;2),在封闭通道中位于Pro-Val-Pro残基及其下游的可能的阻塞位点的识别;3),通道开放和关闭途径的差异;4),瞬态中间结构亚态的证据。结果还表明,在计算上易于处理的模拟时间内可以生成开闭过程中可能的中间构象。

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