Hegde R S, Lingappa V R
Department of Physiology, University of California, San Francisco San Francisco, CA 94143, USA.
Cell. 1996 Apr 19;85(2):217-28. doi: 10.1016/s0092-8674(00)81098-3.
Tight docking of the ribosome at the translocation channel ensures that nascent secretory proteins are shielded from the cytoplasm during transfer into the endoplasmic reticulum. Discrete pause transfer sequences mediate the transient stopping of translocation in certain proteins. Here we show that during a translocational pause, the junction between the ribosome and translocation channel is opened, exposing the nascent chain to the cytosol. While transient, this opening is sufficient to demonstrate macromolecular interactions between the translocating chain and molecules added to the cytosol, such as antibodies and site-specific proteases. Moreover, this opening is accompanied by alterations in the proteins that neighbor the nascent chain. These results demonstrate that specific sequences within a translocating nascent chain can elicit dramatic and reversible structural changes in the translocation machinery. Thus, the translocon is dynamic and can be regulated.
核糖体在转位通道处的紧密对接确保新生分泌蛋白在转移到内质网的过程中免受细胞质的影响。离散的暂停转移序列介导某些蛋白质转位的短暂停止。我们在此表明，在转位暂停期间，核糖体与转位通道之间的连接打开，使新生链暴露于细胞质中。虽然这种开放是短暂的，但足以证明正在转位的链与添加到细胞质中的分子（如抗体和位点特异性蛋白酶）之间的大分子相互作用。此外，这种开放伴随着新生链附近蛋白质的改变。这些结果表明，正在转位的新生链中的特定序列可以引发转位机制中显著且可逆的结构变化。因此，转位子是动态的且可被调节。
