Substitution of putative half-cystine residues in heparin-binding fibroblast growth factor receptors. Loss of binding activity in both two and three loop isoforms.
Substitution of putative half-cystine residues in heparin-binding fibroblast growth factor receptors. Loss of binding activity in both two and three loop isoforms.
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DOI：
10.1016/s0021-9258(19)37115-7
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发表时间：
1992-09
期刊：
影响因子：
--
通讯作者：
J. Hou;M. Kan;F. Wang;J. Xu;M. Nakahara;G. McBride;K. Mckeehan;W. Mckeehan
中科院分区：
文献类型：
--
作者：
J. Hou;M. Kan;F. Wang;J. Xu;M. Nakahara;G. McBride;K. Mckeehan;W. Mckeehan
交替使用编码 89 个残基 NH2 末端免疫球蛋白样二硫键环的外显子，可产生肝素结合成纤维细胞生长因子受体 (FGF-R) 的亚型，在胞外域中具有三个 (FGF-R α) 和两个 (FGF-R β) Ig 样环。 FGF-R α 和 FGF-R β 亚型均表现出性质相似的配体结合活性。在本报告中，我们通过定点诱变和对转染细胞中配体结合活性的分析表明，可能在近膜环 II 或 III 中形成环内二硫键的半胱氨酸的取代破坏了 FGF-R α 和 FGF-R β 亚型中配体结合位点的成熟和形成。编码与缺陷环 III 相邻的完整环 I 和 II 的三环 FGF-R α 构建体以及由缺陷环 II 分隔的完整环 I 和 III 均未表现出配体结合活性。此外，串联环 I 和 III 的双环分子没有活性。结果表明 FGF-R 的单个环 I、II 或 III 不足以形成配体结合位点。环 I 不与环 II 或环 III 形成独立的配体结合位点，但与环 II 和 III 形成的共同配体结合位点相互作用（Xu, J.、Nakahara, M.、Crabb, J. W.、Shi, E.、Matuo, Y.、Fraser, M.、Kan, M.、Hou, J. 和 McKeehan, W. L. (1992) J. Biol. Chem. 267, 17792-17803, 1992)。
Alternate use of an exon coding for an 89-residue NH2 terminal immunoglobulin-like disulfide loop results in isoforms of the heparin-binding fibroblast growth factor receptor (FGF-R) with three (FGF-R alpha) and two (FGF-R beta) Ig-like loops in the extracellular domain. Both FGF-R alpha and FGF-R beta isoforms exhibit qualitatively similar ligand-binding activities. In this report, we show by site-directed mutagenesis and analysis of ligand-binding activity in transfected cells that substitution of a cysteine that potentially forms an intra-loop disulfide in either juxtamembrane Loop II or III disrupted maturation and formation of the ligand-binding site in both FGF-R alpha and FGF-R beta isoforms. Neither three loop FGF-R alpha constructions coding for intact Loops I and II adjacent to defective Loop III nor intact Loops I and III separated by defective Loop II exhibited ligand-binding activity. In addition, a two-loop molecule of tandem Loops I and III was inactive. The results suggest that single Loops I, II, or III of FGF-R are insufficient to form a ligand-binding site. Loop I does not form an independent ligand-binding site with either Loop II or III, but interacts with a common ligand-binding site formed by Loops II and III (Xu, J., Nakahara, M., Crabb, J. W., Shi, E., Matuo, Y., Fraser, M., Kan, M., Hou, J., and McKeehan, W. L. (1992) J. Biol. Chem. 267, 17792-17803, 1992).