Orchansky P L, Escobedo J A, Williams L T
Howard Hughes Medical Institute, University of California, San Francisco 94143-0724.
J Biol Chem. 1988 Oct 15;263(29):15159-65.
The platelet-derived growth factor (PDGF) receptor is usually anchored to the plasma membrane through a membrane-spanning hydrophobic amino acid sequence that splits the molecule into two approximately equal pieces, an amino-terminal external domain that contains the binding site for PDGF and a carboxyl-terminal cytoplasmic domain that includes the tyrosine kinase coding sequences. Here we report the expression of a truncated PDGF receptor that consists of the extracellular domain without the transmembrane and cytoplasmic domains. Unexpectedly, this form of the receptor that lacks a hydrophobic membrane-anchoring sequence was bound to the membrane and was not secreted into the culture media. Conventional methods to dissociate noncovalent protein-protein interactions failed to release the protein from the membrane. When the transmembrane and cytoplasmic sequences were artificially deleted from the PDGF receptor, the truncated extracellular domain was anchored to the membrane through phospholipids and could be released by phospholipase C treatment. This truncated form of the receptor bound PDGF with an affinity 5-20-fold lower than the full-length receptor.
血小板衍生生长因子（PDGF）受体通常通过一个跨膜疏水氨基酸序列锚定在质膜上，该序列将分子分成两个大致相等的部分，一个氨基末端胞外结构域，其包含PDGF的结合位点，以及一个羧基末端胞质结构域，其包括酪氨酸激酶编码序列。在此我们报告一种截短型PDGF受体的表达，该受体由不含跨膜和胞质结构域的胞外结构域组成。出乎意料的是，这种缺乏疏水膜锚定序列的受体形式与膜结合，并未分泌到培养基中。解离非共价蛋白质-蛋白质相互作用的常规方法未能使该蛋白质从膜上释放。当从PDGF受体人工删除跨膜和胞质序列时，截短的胞外结构域通过磷脂锚定在膜上，并且可以通过磷脂酶C处理释放。这种截短形式的受体与PDGF结合的亲和力比全长受体低5至20倍。
