Erat Michèle C, Slatter David A, Lowe Edward D, Millard Christopher J, Farndale Richard W, Campbell Iain D, Vakonakis Ioannis
Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom.
Proc Natl Acad Sci U S A. 2009 Mar 17;106(11):4195-200. doi: 10.1073/pnas.0812516106. Epub 2009 Feb 27.
Collagen and fibronectin are major components of vertebrate extracellular matrices. Their association and distribution control the development and properties of diverse tissues, but thus far no structural information has been available for the complex formed. Here, we report binding of a peptide, derived from the alpha(1) chain of type I collagen, to the gelatin-binding domain of human fibronectin and present the crystal structure of this peptide in complex with the (8-9)FnI domain pair. Both gelatin-binding domain subfragments, (6)FnI(1-2)FnII(7)FnI and (8-9)FnI, bind the same specific sequence on D-period 4 of collagen I alpha(1), adjacent to the MMP-1 cleavage site. (8-9)FnI also binds the equivalent sequence of the alpha(2) chain. The collagen peptide adopts an antiparallel beta-strand conformation, similar to structures of proteins from pathogenic bacteria bound to FnI domains. Analysis of the type I collagen sequence suggests multiple putative fibronectin-binding sites compatible with our structural model. We demonstrate, by kinetic unfolding experiments, that the triple-helical collagen state is destabilized by (8-9)FnI. This finding suggests a role for fibronectin in collagen proteolysis and tissue remodeling.
胶原蛋白和纤连蛋白是脊椎动物细胞外基质的主要成分。它们的结合和分布控制着多种组织的发育和特性，但迄今为止，尚未获得有关所形成复合物的结构信息。在此，我们报道了一种源自I型胶原蛋白α(1)链的肽与人类纤连蛋白的明胶结合结构域的结合，并展示了该肽与(8-9)FnI结构域对形成复合物的晶体结构。明胶结合结构域的两个亚片段，即(6)FnI(1-2)FnII(7)FnI和(8-9)FnI，均与I型胶原蛋白α(1)的D周期4上紧邻基质金属蛋白酶-1切割位点的相同特定序列结合。(8-9)FnI还与α(2)链的等效序列结合。胶原蛋白肽采用反平行β链构象，类似于与FnI结构域结合的致病细菌蛋白质的结构。对I型胶原蛋白序列的分析表明，存在多个与我们的结构模型相符的假定纤连蛋白结合位点。我们通过动力学解折叠实验证明，(8-9)FnI会使三螺旋胶原蛋白状态不稳定。这一发现表明纤连蛋白在胶原蛋白蛋白水解和组织重塑中发挥作用。
