Pepin M C, Beauchemin M, Plamondon J, O'Connor-McCourt M D
Biotechnology Research Institute, National Research Council Canada, Montreal, PQ.
Proc Natl Acad Sci U S A. 1994 Jul 19;91(15):6997-7001. doi: 10.1073/pnas.91.15.6997.
Transforming growth factor beta (TGF-beta) receptor type III is a membrane-anchored proteoglycan that binds TGF-beta via the core protein. We have determined, by deletion mutagenesis of the receptor type III, the minimal essential region of the extracellular domain that is capable of binding TGF-beta. Nine deletion mutants were produced, six of which are expressed on the cell surface and bind TGF-beta. We find that the shortest of these active mutants, which retains only 253 of the 785 amino acids of the extracellular domain, binds TGF-beta with the same affinity as the full-length receptor. These results indicate that the ligand binding domain lies proximal to the transmembrane domain and is functionally independent from the rest of the extracellular domain. We have determined from the mutants that one of the potential glycosaminoglycan attachment sites in the receptor type III is not utilized. Results from the nonglycosylated mutants confirm that the glycosaminoglycan chains are not required for the folding, targeting, and TGF-beta binding activity of the receptor. Moreover, we present evidence for dimerization and multimerization of the receptor.
转化生长因子β（TGF-β）Ⅲ型受体是一种通过核心蛋白结合TGF-β的膜锚定蛋白聚糖。我们通过对Ⅲ型受体进行缺失诱变，确定了细胞外结构域中能够结合TGF-β的最小必需区域。构建了9个缺失突变体，其中6个在细胞表面表达并结合TGF-β。我们发现，这些活性突变体中最短的一个，仅保留了细胞外结构域785个氨基酸中的253个，其结合TGF-β的亲和力与全长受体相同。这些结果表明，配体结合结构域位于跨膜结构域附近，并且在功能上独立于细胞外结构域的其余部分。我们从突变体中确定，Ⅲ型受体中一个潜在的糖胺聚糖附着位点未被利用。非糖基化突变体的结果证实，糖胺聚糖链对于受体的折叠、靶向和TGF-β结合活性并非必需。此外，我们提供了受体二聚化和多聚化的证据。
