CRYSTALLOGRAPHIC REFINEMENT OF RICIN TO 2.5-A
CRYSTALLOGRAPHIC REFINEMENT OF RICIN TO 2.5-A
复制标题
DOI：
10.1002/prot.340100308
复制
发表时间：
1991-01-01
期刊：
影响因子：
--
通讯作者：
ROBERTUS, JD
中科院分区：
文献类型：
--
作者：
RUTENBER, E;KATZIN, BJ;ROBERTUS, JD
植物细胞毒素蓖麻毒素由两条二硫键连接的链组成，每条链约30,000道尔顿。一个基于2.8埃的MIR电子密度图的初始模型已经根据2.5埃的数据通过几轮手工重建结合约束最小二乘算法或分子动力学(XploR)进行了修正。最后一个模型(9)的R因子为21.6%，与标准键长和键角的均方根偏差分别为0.021埃和4.67度。改进需要原始模型中的几个肽片段沿电子密度进行平移调整。此外，还进行了一系列范围较小的修改。主链原子与模型9的均方根偏差为1.89埃。事实证明，分子动力学是一种非常强大的改进工具。然而，测试表明，它不能取代人工干预进行调整，如对多肽链进行局部翻译。R因子并不是一个完全令人满意的改进进展指标；如果仔细观察，差异傅里叶可能是一个更好的监测指标。
The plant cytotoxin ricin consists of two disulfide-linked chains, each of about 30,000 daltons. An initial model based on a 2.8 angstrom MIR electron density map has been refined against 2.5 angstrom data using rounds of hand rebuilding coupled with either a restrained least squares algorithm or molecular dynamics (XPLOR). The last model (9) has an R factor of 21.6% and RMS deviations from standard bond lengths and angles of 0.021 angstrom and 4.67-degrees, respectively. Refinement required several peptide segments in the original model to be adjusted translationally along the electron density. A wide range of lesser changes were also made. The RMS deviation of backbone atoms between the original and model 9 was 1.89 angstrom. Molecular dynamics proved to be a very powerful refinement tool. However, tests showed that it could not replace human intervention in making adjustments such as local translations of the peptide chain. The R factor is not a completely satisfactory indicator of refinement progress; difference Fouriers, when observed carefully, may be a better monitor.