Department of Haematology, University of Cambridge, Cambridge Institute for Medical Research, Cambridge Biomedical Campus, The Keith Peters Building, Hills Road, Cambridge CB2 0XY, United Kingdom.
Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley National Laboratory (LBNL), Building 33R0349, Berkeley, CA 94720-8235, USA.
Acta Crystallogr D Struct Biol. 2022 Nov 1;78(Pt 11):1303-1314. doi: 10.1107/S2059798322010026. Epub 2022 Oct 27.
AlphaFold has recently become an important tool in providing models for experimental structure determination by X-ray crystallography and cryo-EM. Large parts of the predicted models typically approach the accuracy of experimentally determined structures, although there are frequently local errors and errors in the relative orientations of domains. Importantly, residues in the model of a protein predicted by AlphaFold are tagged with a predicted local distance difference test score, informing users about which regions of the structure are predicted with less confidence. AlphaFold also produces a predicted aligned error matrix indicating its confidence in the relative positions of each pair of residues in the predicted model. The phenix.process_predicted_model tool downweights or removes low-confidence residues and can break a model into confidently predicted domains in preparation for molecular replacement or cryo-EM docking. These confidence metrics are further used in ISOLDE to weight torsion and atom-atom distance restraints, allowing the complete AlphaFold model to be interactively rearranged to match the docked fragments and reducing the need for the rebuilding of connecting regions.
AlphaFold 最近成为通过 X 射线晶体学和 cryo-EM 进行实验结构测定的重要工具。预测模型的大部分通常接近实验确定结构的准确性,尽管通常存在局部误差和结构域相对取向的误差。重要的是,由 AlphaFold 预测的蛋白质模型中的残基被标记有预测的局部距离差异测试分数,使用户了解结构的哪些区域预测的置信度较低。AlphaFold 还生成了一个预测的对齐误差矩阵,指示其对预测模型中每对残基相对位置的置信度。phenix.process_predicted_model 工具降低或去除低置信度残基,并可以将模型分解为可预测的结构域,为分子置换或 cryo-EM 对接做准备。这些置信度指标进一步用于 ISOLDE 中,以加权扭转和原子-原子距离约束,允许完整的 AlphaFold 模型进行交互式重排以匹配对接片段,并减少对连接区域重建的需求。