Crowley K S, Reinhart G D, Johnson A E
Department of Chemistry and Biochemistry, University of Oklahoma, Norman 73019.
Cell. 1993 Jun 18;73(6):1101-15. doi: 10.1016/0092-8674(93)90640-c.
The signal sequence is in an aqueous milieu at an early stage in the translocation of a nascent secretory protein across the endoplasmic reticulum membrane. This was determined using fluorescent probes incorporated into the signal sequence of fully assembled ribosome-nascent chain-membrane complexes: the fluorescence lifetimes revealed that the probes were in an aqueous environment rather than buried in the nonpolar core of the membrane. Since these membrane-bound probes were not susceptible to collisional quenching by iodide ions, the space containing the signal sequence is sealed off from the cytoplasm by a tight ribosome-membrane junction. The nascent chain inside the ribosome is also not exposed to the cytoplasm and apparently passes through an aqueous tunnel in the ribosome.
在新生分泌蛋白跨内质网膜转运的早期阶段，信号序列处于水性环境中。这是通过将荧光探针掺入完全组装的核糖体 - 新生链 - 膜复合物的信号序列中来确定的：荧光寿命表明探针处于水性环境中，而不是埋在膜的非极性核心中。由于这些膜结合探针不易受到碘离子的碰撞猝灭，含有信号序列的空间通过紧密的核糖体 - 膜连接与细胞质隔开。核糖体内部的新生链也不暴露于细胞质，并且显然通过核糖体中的水性通道。
