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arXiv 1208.2680q-bio.BM
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基于RNA启发的分析方法对蛋白质环结构的原子精度预测

Atomic-accuracy prediction of protein loop structures through an RNA-inspired ansatz

Rhiju Das

摘要:

一致性预测生物聚合物结构在原子分辨率单独从序列仍然是一个困难的问题,即使是小的子段的大蛋白质。在比较建模和蛋白质设计中经常出现的这种环预测挑战,当环长度超过10个残基并且如果周围的侧链构象被擦除,则可能变得难以处理。本文介绍了一种基于“逐步ansatz”的建模策略,最近开发的RNA建模,假定任何现实的全原子分子构象可以建立由残基的残基逐步枚举。当利用Rosetta框架中的动态编程类递归时,所得到的逐步组装(SWA)协议能够以数千CPU小时的显著但可实现的成本对12个残基循环进行枚举采样。在先前建立的基准中,SWA恢复了20个循环中19个循环的亚埃精度的晶体学构象,而KIC建模的20个循环中有14个循环的计算能力相当。此外,SWA对生物学文献中突出显示的另外一组15个环给出了高准确度结果,因为它们的不规则性或不寻常的长度。成功的例子包括顺式-Pro接触转角、穿过其他侧链隧道的环和长度高达24个残基的环。剩余的问题情况下,罗塞塔所有原子能量函数的不准确性。在另外五个盲测中,SWA实现了亚埃精度模型,包括在蛋白质/RNA结合界面中的首次成功,即第四次RNA谜题竞赛中的YbxF/扭结-转弯相互作用。这些结果建立了全原子计数作为蛋白质结构的系统方法,可以利用高性能计算和物理上真实的能量函数来更一致地实现原子分辨率。

英文摘要:

Consistently predicting biopolymer structure at atomic resolution from sequence alone remains a difficult problem, even for small sub-segments of large proteins. Such loop prediction challenges, which arise frequently in comparative modeling and protein design, can become intractable as loop lengths exceed 10 residues and if surrounding side-chain conformations are erased. This article introduces a modeling strategy based on a 'stepwise ansatz', recently developed for RNA modeling, which posits that any realistic all-atom molecular conformation can be built up by residue-by-residue stepwise enumeration. When harnessed to a dynamic-programming-like recursion in the Rosetta framework, the resulting stepwise assembly (SWA) protocol enables enumerative sampling of a 12 residue loop at a significant but achievable cost of thousands of CPU-hours. In a previously established benchmark, SWA recovers crystallographic conformations with sub-Angstrom accuracy for 19 of 20 loops, compared to 14 of 20 by KIC modeling with a comparable expenditure of computational power. Furthermore, SWA gives high accuracy results on an additional set of 15 loops highlighted in the biological literature for their irregularity or unusual length. Successes include cis-Pro touch turns, loops that pass through tunnels of other side-chains, and loops of lengths up to 24 residues. Remaining problem cases are traced to inaccuracies in the Rosetta all-atom energy function. In five additional blind tests, SWA achieves sub-Angstrom accuracy models, including the first such success in a protein/RNA binding interface, the YbxF/kink-turn interaction in the fourth RNA-puzzle competition. These results establish all-atom enumeration as a systematic approach to protein structure that can leverage high performance computing and physically realistic energy functions to more consistently achieve atomic resolution.

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