Monson J M, Borstein P
Proc Natl Acad Sci U S A. 1973 Dec;70(12):3521-5. doi: 10.1073/pnas.70.12.3521.
Chick cranial-bone procollagen, extracted at neutral pH in the presence of inhibitors of proteolytic enzymes, exists as a triple-stranded protein with disulfide bonds linking all three chains. The biosynthetic precursor function of this procollagen was demonstrated by pulsechase experiments. The ratio of radioactive hydroxyproline to proline in proalpha chains obtained by reduction and alkylation of the disulfide-bonded precursor was similar to the value determined for proalpha1 from acid-extracted procollagen. However, the molecular weight of these chains was higher than that previously determined for proalpha1 and proalpha2, suggesting that extraction of tissue at low pH results in a selective loss of disulfide-bonded regions from procollagen. These findings reconcile several apparently conflicting reports on the nature of procollagen identified in bone and in the medium of cultured fibroblasts and indicate that in both systems procollagen is synthesized as a disulfidelinked protein.
在存在蛋白水解酶抑制剂的中性pH条件下提取的鸡颅骨前胶原，以三链蛋白形式存在，所有三条链通过二硫键相连。通过脉冲追踪实验证明了这种前胶原的生物合成前体功能。通过对二硫键连接的前体进行还原和烷基化得到的前α链中放射性羟脯氨酸与脯氨酸的比率，与从酸提取的前胶原中测定的前α1的值相似。然而，这些链的分子量高于先前测定的前α1和前α2的分子量，这表明在低pH条件下提取组织会导致前胶原中二硫键连接区域的选择性丢失。这些发现调和了关于在骨和培养成纤维细胞培养基中鉴定的前胶原性质的几份明显相互矛盾的报告，并表明在这两个系统中，前胶原都是作为二硫键连接的蛋白质合成的。
