Emtner M, Roos P
Department of Biochemistry, University of Uppsala, Biomedical Center, Sweden.
Acta Endocrinol (Copenh). 1990 Aug;123(2):231-7. doi: 10.1530/acta.0.1230231.
Some properties of cytosolic receptors of the lactogenic type from female rat liver were studied and compared with those of membrane-bound (microsomal) receptors. The association constant between the cytosolic receptors and human growth hormone was 2.2 l/nmol, which was not significantly different from the value obtained for the microsomal receptors (3.6 l/nmol). Since unlabeled hGH and human prolactin, but not bovine growth hormone, displaced [125I]hGH bound to receptors from both sources, the cytosolic receptors, like the microsomal receptors, must be lactogenic. Furthermore, the cytosolic receptors were recognized by a monoclonal antibody raised against microsomal receptors from female rat liver. However, covalent cross-linking of cytosolic receptors to [125I]hGH and subsequent sodium dodecyl sulphate electrophoresis gave a single band corresponding to a molecular weight of 42,200 (after subtraction of the molecular weight of hGH), which differs significantly (p less than 0.01) from the values determined for the two distinct bands given by the microsomal fraction. Moreover, upon molecular sieve chromatography the receptor activity in the two fractions appeared at significantly (p less than 0.05) different elution volumes. These results show that the cytosolic and microsomal receptors have some structural features in common but are definitely not identical.
对雌性大鼠肝脏中催乳素型胞质受体的一些特性进行了研究，并与膜结合（微粒体）受体的特性进行了比较。胞质受体与人生长激素之间的结合常数为2.2 l/nmol，与微粒体受体获得的值（3.6 l/nmol）无显著差异。由于未标记的hGH和人催乳素，而非牛生长激素，能取代与两种来源受体结合的[125I]hGH，因此胞质受体与微粒体受体一样，必定是催乳素型的。此外，胞质受体能被针对雌性大鼠肝脏微粒体受体产生的单克隆抗体识别。然而，胞质受体与[125I]hGH的共价交联以及随后的十二烷基硫酸钠电泳产生了一条对应分子量为42,200的单带（减去hGH的分子量后），这与微粒体部分给出的两条不同带的测定值有显著差异（p小于0.01）。此外，在分子筛色谱上，两个部分的受体活性出现在显著不同（p小于0.05）的洗脱体积处。这些结果表明，胞质受体和微粒体受体有一些共同的结构特征，但肯定不完全相同。
