Semi-Rigid Solution Structures of Heparin by Constrained X-ray Scattering Modelling: New Insight into Heparin-Protein Complexes
Semi-Rigid Solution Structures of Heparin by Constrained X-ray Scattering Modelling: New Insight into Heparin-Protein Complexes
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DOI：
10.1016/j.jmb.2009.10.064
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发表时间：
2010-01-22
影响因子：
5.6
通讯作者：
Perkins, Stephen J.
中科院分区：
文献类型：
--
作者：
Khan, Sanaullah;Gor, Jayesh;Perkins, Stephen J.
阴离子多糖肝素和硫酸乙酰肝素在许多生理过程的调节中起重要作用。肝素通常用作硫酸乙酰肝素的类似物。尽管已知短肝素片段的肝素-蛋白质复合物的NMR溶液结构和19种晶体结构，但迄今为止尚未报道较大肝素片段的结构。在这里，我们表明，6个纯化的肝素片段dp 6-dp 36（其中dp代表聚合度）的溶液结构可以通过分析超离心，同步加速器X射线散射和约束建模的组合来确定。dp 6-dp 36的分析超离心速度数据显示沉降系数随尺寸从1.09 S线性增加到1.84 S。dp 6-dp 36的X射线散射给出了回转半径RC;其范围为1.33 nm至3.12 nm，最大长度范围为3.0 nm至12.3 nm。X射线散射的较高分辨率显示肝素的弯曲随着尺寸的增加而增加。5000个随机肝素构象的约束分子建模导致dp 18、dp 24、dp 30和dp 36中的每一个的9-15个最佳拟合结构，这表明柔性和轻度弯曲结构中存在短线性段。将这些溶液结构与肝素-蛋白质复合物的晶体结构进行比较，发现艾杜糖醛酸和葡糖胺环之间的phi（phi）和psi（psi）角范围相似。我们的结论是，肝素在溶液中有一个半刚性和扩展的构象，其最佳的结合蛋白质的目标，而没有重大的构象变化。(C)2009爱思唯尔有限公司保留所有权利。
The anionic polysaccharides heparin and heparan sulphate play essential roles in the regulation of many physiological processes. Heparin is often used as an analogue for heparan sulphate. Despite knowledge of an NMR solution structure and 19 crystal structures of heparin-protein complexes for short heparin fragments, no structures for larger heparin fragments have been reported up to now. Here, we show that solution structures for six purified heparin fragments dp6-dp36 (where dp stands for degree of polymerisation) can be determined by a combination of analytical ultracentrifugation, synchrotron X-ray scattering, and constrained modelling Analytical ultracentrifugation velocity data for dp6-dp36 showed sedimentation coefficients that increased linearly from 1.09 S to 1.84 S with size. X-ray scattering of dp6-dp36 gave radii of gyration RC; that ranged from 1.33 nm to 3.12 nm and maximum lengths that ranged from 3.0 nm to 12.3 nm. The higher resolution of X-ray scattering revealed an increased bending of heparin with increased size. Constrained molecular modelling of 5000 randomised heparin conformers resulted in 9-15 best-fit structures for each of dp18, dp24, dp30, and dp36 that indicated flexibility and the presence of short linear segments in mildly bent structures. Comparisons of these solution structures with crystal structures of heparin-protein complexes revealed similar ranges of phi (phi) and psi (psi) angles between iduronate and glucosamine rings. We conclude that heparin in solution has a semi-rigid and extended conformation that is preformed for its optimal binding to protein targets without major conformational changes. (C) 2009 Elsevier Ltd. All rights reserved.