Tong P Y, Tollefsen S E, Kornfeld S
Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110.
J Biol Chem. 1988 Feb 25;263(6):2585-8.
The bovine cation-independent mannose 6-phosphate receptor (CI-MPR) and the human insulin-like growth factor II (IGF-II) receptor have recently been shown to be 80% identical in their amino acid sequences as deduced from cDNA clones (Morgan, D. O., Edman, J. C., Standring, D. N., Fried, V. A., Smith, M. C., Roth, R. A., and Rutter, W. J. (1987) Nature 329, 301-307). We have studied the binding of IGF-II to affinity-purified CI-MPR in order to obtain direct evidence that the same protein binds mannose 6-phosphate-containing ligands and IGF-II. In equilibrium binding studies, the CI-MPR bound 0.95 mol of IGF-II/mol of receptor with a Kd of 0.2 nM. The pH optimum of binding was 7.4. The addition of mannose 6-phosphate did not affect binding, indicating that the two ligands interact with different binding sites on the receptor. IGF-I bound to the receptor with a much lower affinity (Kd of 0.4 microM), and insulin binding could not be detected. IGF-II did not bind to the cation-dependent mannose 6-phosphate receptor. We conclude that the cation-independent mannose 6-phosphate receptor and the IGF-II receptor are the same protein.
最近的研究表明，从cDNA克隆推导的牛不依赖阳离子的甘露糖6-磷酸受体（CI-MPR）和人胰岛素样生长因子II（IGF-II）受体的氨基酸序列有80%的同源性（摩根，D.O.，埃德曼，J.C.，斯坦德林，D.N.，弗里德，V.A.，史密斯，M.C.，罗斯，R.A.，和鲁特，W.J.（1987）《自然》329，301 - 307）。我们研究了IGF-II与亲和纯化的CI-MPR的结合，以获得直接证据证明同一蛋白能结合含甘露糖6-磷酸的配体和IGF-II。在平衡结合研究中，CI-MPR以0.2 nM的Kd结合0.95摩尔的IGF-II/摩尔受体。结合的最适pH为7.4。添加甘露糖6-磷酸不影响结合，表明这两种配体与受体上不同的结合位点相互作用。IGF-I以低得多的亲和力（Kd为0.4 microM）结合到受体上，且未检测到胰岛素结合。IGF-II不与依赖阳离子的甘露糖6-磷酸受体结合。我们得出结论，不依赖阳离子的甘露糖6-磷酸受体和IGF-II受体是同一蛋白。
