Nanostructure of fibrillin-1 reveals compact conformation of EGF arrays and mechanism for extensibility
Nanostructure of fibrillin-1 reveals compact conformation of EGF arrays and mechanism for extensibility
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DOI：
10.1073/pnas.0601609103
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发表时间：
2006-08-08
影响因子：
11.1
通讯作者：
Wess, Tim J.
中科院分区：
文献类型：
--
作者：
Baldock, Clair;Siegler, Veronique;Wess, Tim J.
纤维蛋白-1是一种330 kDa的多域细胞外基质蛋白，聚合形成57 nm的周期性微纤维，对所有组织的弹性都是必不可少的。纤毛素-1是钙结合的EGF重复序列家族的成员之一，是结构分析的原型。然而，由于分子的复杂性和EGF阵列对结晶的抵抗，对纤毛素-1的详细结构和它在微原纤维中的组织都知之甚少。在这里，我们使用小角X射线散射和光散射来分析人纤维蛋白-1的溶液结构，并产生覆盖90%分子的重叠片段的从头算结构。散射数据显示了钙结合EGF阵列在溶液中的非线性构象，而不是像目前模型预测的那样呈现均匀的棒状。这一发现对许多其他含有EGF的细胞外基质和膜蛋白的结构具有重要意义。散射数据还突出了纤维蛋白-1分子的一个非常紧密的球状区域，该区域包含整合素和硫酸乙酰肝素结合部位。通过使用电子显微镜和单粒子图像分析计算该区域的3D重建，这一发现得到了证实。总而言之，这些数据使得能够产生用于微原纤维组织的改进模型和先前未描述的微原纤维延伸性的机制。
Fibrillin-1 is a 330-kDa multidomain extracellular matrix protein that polymerizes to form 57-nm periodic microfibrils, which are essential for all tissue elasticity. Fibrillin-1 is a member of the calcium-binding EGF repeat family and has served as a prototype for structural analyses. Nevertheless, both the detailed structure of fibrillin-1 and its organization within microfibrils are poorly understood because of the complexity of the molecule and the resistance of EGF arrays to crystallization. Here, we have used small-angle x-ray scattering and light scattering to analyze the solution structure of human fibrillin-1 and to produce ab initio structures of overlapping fragments covering 90% of the molecule. Rather than exhibiting a uniform rod shape as current models predict, the scattering data revealed a nonlinear conformation of calcium-binding EGF arrays in solution. This finding has major implications for the structures of the many other EGF-containing extracellular matrix and membrane proteins. The scattering data also highlighted a very compact, globular region of the fibrillin-1 molecule, which contains the integrin and heparan sulfate-binding sites. This finding was confirmed by calculating a 3D reconstruction of this region using electron microscopy and single-particle image analysis. Together, these data have enabled the generation of an improved model for microfibril organization and a previously undescribed mechanism for microfibril extensibility.