Talmadge K, Gilbert W
Proc Natl Acad Sci U S A. 1982 Mar;79(6):1830-3. doi: 10.1073/pnas.79.6.1830.
We study the biosynthesis of preproinsulin and proinsulin in Escherichia coli by pulse-chase experiments. When E. coli is transformed with plasmids bearing a gene consisting of a fusion of preproinsulin DNA to part or to all of the DNA encoding a bacterial signal sequence, a variety of hybrid preproinsulin molecules can be made. Molecules with largely complete hybrid signal sequences are secreted into the periplasm. Molecules with defective signal sequences, lacking the hydrophobic core, are not secreted and remain in the cytoplasm. Such molecules are degraded with a 2-min half-life, whereas the molecules transported to the periplasm are at least 10 times more stable. A full-length preproinsulin precursor appears transiently before the signal sequence is cleaved off by the bacterial signal peptidase, and we propose a model to account for this.
我们通过脉冲追踪实验研究了大肠杆菌中胰岛素原前体和胰岛素原的生物合成。当用携带由胰岛素原前体DNA与编码细菌信号序列的部分或全部DNA融合而成的基因的质粒转化大肠杆菌时，可以产生多种杂合胰岛素原前体分子。具有基本完整杂合信号序列的分子被分泌到周质中。信号序列有缺陷、缺乏疏水核心的分子不被分泌，留在细胞质中。这类分子以2分钟的半衰期被降解，而转运到周质中的分子稳定性至少高10倍。全长胰岛素原前体在被细菌信号肽酶切割掉信号序列之前短暂出现，我们提出了一个模型来解释这一现象。
