论文部分内容阅读
1980年,在大鼠和小鼠垂体中发现了裂解型催乳素(cleaved prolactin)。完整的催乳素(PRL)分子含有三个二硫键,分子内部形成一个大环和两个小环。裂解型PRL分子内二硫键大环中出现一个断口,处于130位和140位两个赖氨酸残基之间,分子中虽出现断口,但大环中二硫键仍保留,因而裂解型PRL仍为一连续分子。当二硫键还原而断裂时,裂解型PRL即断裂成两个片段,按其分子量大小分别称为16K片段(N端)和8K片段(C端)。裂解型PRL与完整PRL的作用不同,前者的16K部分能诱发乳腺上皮细胞DNA合成和细胞分裂,为一种促乳腺有丝分裂因子;后者则促进乳汁特异性蛋白质合成。
In 1980, cleaved prolactin was found in the pituitary of rats and mice. The intact prolactin (PRL) molecule contains three disulfide bonds, forming a macrocycle and two small loops inside the molecule. In the cleavage-type PRL intramolecular disulfide bond macroscopically, there is a fracture between the two lysine residues at position 130 and 140. Although there is a break in the molecule, disulfide bonds remain in the macrocycle, PRL is still a continuous molecule. When the disulfide bond is reduced and cleaved, the cleaved PRL breaks into two fragments, referred to as the 16K fragment (N-terminal) and the 8K fragment (C-terminal), respectively, according to their molecular weight. Cleaved PRL is different from intact PRL in that the 16K portion of the former induces DNA synthesis and cell division in breast epithelial cells, a pro-mitotic factor that promotes mammary gland-specific protein synthesis.