Terwilliger Thomas C
Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
Acta Crystallogr D Biol Crystallogr. 2010 Mar;66(Pt 3):268-75. doi: 10.1107/S0907444910000314. Epub 2010 Feb 12.
A method for the identification of alpha-helices in electron-density maps at low resolution followed by interpretation at moderate to high resolution is presented. Rapid identification is achieved at low resolution, where alpha-helices appear as tubes of density. The positioning and direction of the alpha-helices is obtained at moderate to high resolution, where the positions of side chains can be seen. The method was tested on a set of 42 experimental electron-density maps at resolutions ranging from 1.5 to 3.8 A. An average of 63% of the alpha-helical residues in these proteins were built and an average of 76% of the residues built matched helical residues in the refined models of the proteins. The overall average r.m.s.d. between main-chain atoms in the modeled alpha-helices and the nearest atom with the same name in the refined models of the proteins was 1.3 A.
本文提出了一种在低分辨率电子密度图中识别α-螺旋，随后在中等到高分辨率下进行解析的方法。在低分辨率下可快速识别α-螺旋，此时α-螺旋表现为密度管。在中等到高分辨率下可确定α-螺旋的位置和方向，此时能够看到侧链的位置。该方法在一组分辨率范围为1.5至3.8 Å的42个实验电子密度图上进行了测试。这些蛋白质中平均63%的α-螺旋残基得以构建，且构建的残基中平均76%与蛋白质精细模型中的螺旋残基匹配。所构建的α-螺旋中主链原子与蛋白质精细模型中最近的同名原子之间的总体平均均方根偏差为1.3 Å。
