Cheung Tsz Ying Sylvia, Fairchild Michael J, Zarivach Raz, Tanentzapf Guy, Van Petegem Filip
Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, Canada.
J Mol Biol. 2009 Apr 10;387(4):787-93. doi: 10.1016/j.jmb.2009.01.053.
Integrins are transmembrane receptors that mediate cell adhesion to the extracellular matrix and play essential roles in tissue development and maintenance. The cytoplasmic segment of integrin associates with talin, a large intracellular protein that links integrin to the actin cytoskeleton. Binding of talin via an integrin binding segment (IBS1) results in large conformational changes in the extracellular portion of integrin, which modulates the affinity of integrins for their extracellular matrix ligands. However, integrin binding also requires a second segment of talin (IBS2). Despite detailed descriptions of the integrin-IBS1 binding, the molecular determinants that drive the integrin-IBS2 association are poorly understood. Here, we describe the crystal structure of the talin IBS2 domain, which forms a five-helix bundle. The large structural homology with a vinculin binding domain hints at an ancient gene duplication and suggests that helix 4 may bind to vinculin if the bundle is unfolded. Mapping previous mutations on the surface highlights a likely binding interface for integrin.
整合素是跨膜受体,介导细胞与细胞外基质的黏附,并在组织发育和维持中发挥重要作用。整合素的细胞质区段与踝蛋白结合,踝蛋白是一种大型细胞内蛋白,将整合素与肌动蛋白细胞骨架相连。通过整合素结合区段(IBS1)与踝蛋白结合会导致整合素细胞外部分发生大的构象变化,从而调节整合素对其细胞外基质配体的亲和力。然而,整合素结合还需要踝蛋白的第二个区段(IBS2)。尽管对整合素-IBS1结合有详细描述,但驱动整合素-IBS2结合的分子决定因素仍知之甚少。在这里,我们描述了踝蛋白IBS2结构域的晶体结构,它形成一个五螺旋束。与纽蛋白结合结构域的高度结构同源性暗示了一个古老的基因复制事件,并表明如果该束展开,螺旋4可能与纽蛋白结合。将先前的突变定位在表面突出了整合素可能的结合界面。