• Cain, Stuart A.
• Wess, Tim J.
• Bax, Daniel V.
• Siegler, Veronique
• Roessle, Manfred
• Baldock, Clair
• Kielty, Cay M.
• Grossmann, J. Günter
• Wang, Ming Chuan
• Haston, J. Louise
• Marson, Andrew
• Mellody, Kieran T.

Abstract

<p>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.</p>

Topics

• impedance spectroscopy
• elasticity
• electron microscopy
• Calcium
• crystallization
• X-ray scattering
• light scattering