Sussman P M, Tushinski R J, Bancroft F C
Proc Natl Acad Sci U S A. 1976 Jan;73(1):29-33. doi: 10.1073/pnas.73.1.29.
Membrane fraction RNA isolated from rat pituitary tumor (GC) cells has been translated in a wheat germ extract. A product was synthesized which was immunologically related to growth hormone, but which migrated more slowly than growth hormone upon sodium dodecyl sulfate-acrylamide gel electrophoresis. The mobility of the cell-free product on gels of this type was unchanged by treatment with either KOH or RNase. The mobilities during paper electrophoresis of the methionine-containing tryptic peptides obtained from the cell-free product were identical to those obtained from growth hormone synthesized and secreted by the GC cells. Molecular weights for growth hormone and the cell-free product of 19,500 and 24,000, respectively, were determined by gel electrophoresis of these proteins together with marker proteins of known molecular weights. No protein with the properties of the cell-free product was detected after a 2 min incubation of the GC cells with [35S]methionine. However, treatment of the GC cells, with a protease inhibitor, L-1-tosylamide-2-phenyl-ethylchloromethyl ketone (TPCK), led to the appearance of a new polypeptide, immunologically related to growth hormone, and with a mobility on gels identical to that of the cell-free product. These results strongly imply that the cell-free product represents a growth hormone precursor (pregrowth hormone) which is rapidly converted to growth hormone in pituitary cells.
从大鼠垂体瘤（GC）细胞中分离出的膜部分RNA已在小麦胚芽提取物中进行了翻译。合成了一种产物，它与生长激素在免疫上相关，但在十二烷基硫酸钠-丙烯酰胺凝胶电泳中迁移速度比生长激素慢。用KOH或核糖核酸酶处理后，这种无细胞产物在这类凝胶上的迁移率没有变化。从无细胞产物中获得的含甲硫氨酸的胰蛋白酶肽在纸上电泳时的迁移率与从GC细胞合成并分泌的生长激素中获得的迁移率相同。通过将这些蛋白质与已知分子量的标记蛋白一起进行凝胶电泳，分别测定了生长激素和无细胞产物的分子量为19,500和24,000。用[35S]甲硫氨酸孵育GC细胞2分钟后，未检测到具有无细胞产物特性的蛋白质。然而，用蛋白酶抑制剂L-1-甲苯磺酰胺-2-苯基-乙基氯甲基酮（TPCK）处理GC细胞，导致出现一种新的多肽，它与生长激素在免疫上相关，并且在凝胶上的迁移率与无细胞产物相同。这些结果强烈表明，无细胞产物代表一种生长激素前体（前生长激素），它在垂体细胞中迅速转化为生长激素。
