Engel J
Department of Biophysical Chemistry, University of Basel, Switzerland.
Int J Biol Macromol. 1991 Jun;13(3):147-51. doi: 10.1016/0141-8130(91)90039-w.
Most proteins of the extracellular matrix (ECM), such as the glycoproteins, collagens and proteoglycans, consist of many structurally autonomous domains that are often functionally distinct. Consequently these proteins are designated as mosaic proteins. Related domains are often found in several different ECM proteins. Domains which are of importance for assembly have been identified by fragmentation and other approaches. Triple-stranded coiled-coil domains in laminin and probably also in tenascin and thrombospondin are responsible for chain selection, a process which may be important for the formation of tissue specific isoforms. Globular domains at the C-terminus of collagenous domains are essential for the registration of the three chains and triple-helix formation. Fibrillar assemblies of these triple helices with constituent globular domains serve important assembly functions in many collagens including collagens IV and VI. Many other domains with more specialized functions in assembly have been identified in laminin, fibronectin and other ECM proteins. Cys-rich domains with either distant or close homology with epidermal growth factor are repeated manifold in rod-like regions of a number of ECM proteins including laminin, tenascin and thrombospondin. They may serve as spacer elements but as suggested for laminin some domains of this type may also function as signals for cellular growth and differentiation. Another important cellular function common to many ECM proteins is cell attachment. Several cell attachment sites have been localized in structurally unrelated domains of the same or of different ECM proteins.
大多数细胞外基质（ECM）蛋白，如糖蛋白、胶原蛋白和蛋白聚糖，由许多结构上自主的结构域组成，这些结构域通常具有不同的功能。因此，这些蛋白质被称为镶嵌蛋白。相关结构域常常在几种不同的ECM蛋白中被发现。通过片段化和其他方法已经鉴定出了对组装很重要的结构域。层粘连蛋白中的三链卷曲螺旋结构域，可能还有腱生蛋白和血小板反应蛋白中的三链卷曲螺旋结构域，负责链的选择，这一过程可能对组织特异性异构体的形成很重要。胶原结构域C端的球状结构域对于三条链的对齐和三螺旋的形成至关重要。这些带有组成性球状结构域的三螺旋的纤维状组装体在包括IV型和VI型胶原在内的许多胶原蛋白中发挥着重要的组装功能。在层粘连蛋白、纤连蛋白和其他ECM蛋白中还鉴定出了许多在组装中具有更特殊功能的其他结构域。与表皮生长因子具有远源或近源同源性的富含半胱氨酸的结构域在包括层粘连蛋白、腱生蛋白和血小板反应蛋白在内的许多ECM蛋白的杆状区域中多次重复出现。它们可能作为间隔元件，但正如对层粘连蛋白所暗示的那样，这种类型的一些结构域也可能作为细胞生长和分化的信号。许多ECM蛋白共有的另一个重要细胞功能是细胞附着。几个细胞附着位点已定位在相同或不同ECM蛋白的结构不相关的结构域中。
