Center for Biomedical Engineering and Technology and Department of Physiology, University of Maryland School of Medicine, University of Maryland, Baltimore 725 W. Lombard St., Baltimore, MD 21201, USA.
Exp Cell Res. 2012 Dec 10;318(20):2543-7. doi: 10.1016/j.yexcr.2012.08.007. Epub 2012 Sep 7.
Fibulins are evolutionarily conserved extracellular matrix (ECM) proteins that assemble in elastic fibers and basement membranes. Caenorhabditis elegans has a single fibulin gene that produces orthologs of vertebrate fibulin-1 C and D splice forms. In a structure-function analysis of fibulin-1 domains, a series of deletion constructs show that EGF repeats 4 and 5 are required for the hemicentin-dependent assembly and function of fibulin-1D in native locations. In contrast, constructs missing the second EGF repeat of fibulin-1D (EGF2D) assemble in ectopic locations in a hemicentin dependent manner. Constructs that contain EGF2D are cleaved into two fragments, but constructs with EGF2D missing are not, suggesting that a protease binds and/or cleaves fibulin-1D at a site that is likely within EGF2D. Together, the data suggests that EGF repeats 4 and 5 promote interaction with hemicentin while a region within EGF2D suppresses ectopic interactions with hemicentin and this suppression may be protease dependent.
纤维结合蛋白是进化上保守的细胞外基质（ECM）蛋白，它们在弹性纤维和基底膜中组装。秀丽隐杆线虫只有一个纤维结合蛋白基因，它产生脊椎动物纤维结合蛋白-1 C 和 D 剪接形式的同源物。在纤维结合蛋白-1 结构功能分析中，一系列缺失构建体表明 EGF 重复 4 和 5 是纤维结合蛋白-1D 在天然位置依赖于半钙蛋白组装和功能所必需的。相比之下，缺失纤维结合蛋白-1D 的第二个 EGF 重复（EGF2D）的构建体以半钙蛋白依赖的方式在异位位置组装。含有 EGF2D 的构建体被切割成两个片段，但缺失 EGF2D 的构建体则不会，这表明一种蛋白酶在可能位于 EGF2D 内的位点结合和/或切割纤维结合蛋白-1D。总之，数据表明 EGF 重复 4 和 5 促进与半钙蛋白的相互作用，而 EGF2D 内的一个区域抑制与半钙蛋白的异位相互作用，这种抑制可能依赖于蛋白酶。
