Crine P, Gossard F, Seidah N G, Blanchette L, Lis M, Chrétien M
Proc Natl Acad Sci U S A. 1979 Oct;76(10):5085-9. doi: 10.1073/pnas.76.10.5085.
In the pars intermedia of rat pituitary glands, two forms of a common precursor for corticotropin (ACTH) and beta-lipotropin with apparent molecular weights of 34,000 and 36,000 were resolved by sodium dodecyl sulfate/acrylamide gradient slab gel electrophoresis. High-performance liquid chromatographic analysis of [35S]methionine-labeled tryptic fragments of the two forms of the precursor revealed that both contained copies of ACTH-(1-8) and beta-lipotropin-(61-69) sequences. When biosynthetic studies were performed in the presence of tunicamycin, the 34,000- and 36,000-dalton forms were replaced by a peptide with an apparent molecular weight of 32,000. It was therefore concluded that the 34,000- and 36,000-dalton forms of the precursor represent two glycoprotein variants of similar polypeptides, differing in the number of asparagine-linked carbohydrate moieties. During pulse-chase incubations with [35S]methionine, the precursor forms were cleaved into two major groups of labeled products: (i) beta-endorphin and (ii) a mixture of ACTH fragments closely related to alpha-melanotropin. No ACTH-(1-39) was found at the end of a 2-hr chase period, suggesting that ACTH is not a significant hormone product of the rat pars intermedia.
在大鼠垂体中间部，通过十二烷基硫酸钠/丙烯酰胺梯度平板凝胶电泳分离出促肾上腺皮质激素（ACTH）和β-促脂素的一种常见前体的两种形式，其表观分子量分别为34,000和36,000。对这两种形式前体的[35S]甲硫氨酸标记的胰蛋白酶片段进行高效液相色谱分析，结果显示二者均含有ACTH-(1-8)和β-促脂素-(61-69)序列的拷贝。当在衣霉素存在的情况下进行生物合成研究时，34,000道尔顿和36,000道尔顿的形式被一种表观分子量为32,000的肽所取代。因此得出结论，34,000道尔顿和36,000道尔顿的前体形式代表相似多肽的两种糖蛋白变体，二者天冬酰胺连接的碳水化合物部分数量不同。在用[35S]甲硫氨酸进行脉冲追踪孵育期间，前体形式被切割成两大类标记产物：（i）β-内啡肽和（ii）与α-促黑素密切相关的ACTH片段混合物。在2小时的追踪期结束时未发现ACTH-(1-39)，这表明ACTH不是大鼠垂体中间部的主要激素产物。
