Battaglia C, Mayer U, Aumailley M, Timpl R
Max-Planck-Institut für Biochemie, Martinsried, Federal Republic of Germany.
Eur J Biochem. 1992 Sep 1;208(2):359-66. doi: 10.1111/j.1432-1033.1992.tb17195.x.
A large, low-density form of heparan sulfate proteoglycan was isolated from the Engelbreth-Holm-Swarm (EHS) tumor and demonstrated to bind in immobilized-ligand assays to laminin fragment E3, collagen type IV, fibronectin and nidogen. The first three ligands mainly recognize the heparan sulfate chains, as shown by inhibition with heparin and heparan sulfate and by the failure to bind to the proteoglycan protein core. Nidogen, obtained from the EHS tumor or in recombinant form, binds exclusively to the protein core in a heparin-insensitive manner. Studies with other laminin fragments indicate that the fragment E3 possesses a unique binding site of laminin for the proteoglycan. A major binding site of nidogen was localized to its central globular domain G2 by using overlapping fragments. This allows for the formation of ternary complexes between laminin, nidogen and proteoglycan, suggesting a key role for nidogen in basement-membrane assembly. Evidence is provided for a second proteoglycan-binding site in the C-terminal globule G3 of nidogen, but this interaction prevents the formation of such ternary complexes. Therefore, the G3-mediated nidogen binding to laminin and proteoglycan are mutually exclusive.
从恩格尔布雷特-霍尔姆-斯旺（EHS）肿瘤中分离出一种大型、低密度形式的硫酸乙酰肝素蛋白聚糖，并在固定配体分析中证明其能与层粘连蛋白片段E3、IV型胶原、纤连蛋白和巢蛋白结合。前三种配体主要识别硫酸乙酰肝素链，这通过肝素和硫酸乙酰肝素的抑制作用以及无法与蛋白聚糖蛋白核心结合得以证明。从EHS肿瘤中获得或以重组形式获得的巢蛋白，以一种对肝素不敏感的方式仅与蛋白核心结合。对其他层粘连蛋白片段的研究表明，片段E3具有层粘连蛋白与蛋白聚糖的独特结合位点。通过使用重叠片段，巢蛋白的一个主要结合位点定位于其中心球状结构域G2。这使得层粘连蛋白、巢蛋白和蛋白聚糖之间能够形成三元复合物，表明巢蛋白在基底膜组装中起关键作用。有证据表明巢蛋白的C末端球状结构域G3中存在第二个蛋白聚糖结合位点，但这种相互作用会阻止此类三元复合物的形成。因此，G3介导的巢蛋白与层粘连蛋白和蛋白聚糖的结合是相互排斥的。
