SYSTEMATIC PROBING OF THE ENVIRONMENT OF A TRANSLOCATING SECRETORY PROTEIN DURING TRANSLOCATION THROUGH THE ER MEMBRANE
SYSTEMATIC PROBING OF THE ENVIRONMENT OF A TRANSLOCATING SECRETORY PROTEIN DURING TRANSLOCATION THROUGH THE ER MEMBRANE
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DOI：
10.1002/j.1460-2075.1994.tb06713.x
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发表时间：
1994-09-01
期刊：
影响因子：
11.4
通讯作者：
RAPOPORT, TA
中科院分区：
文献类型：
--
作者：
MOTHES, W;PREHN, S;RAPOPORT, TA
我们扩展了一种先前开发的光交联方法，以系统地探究分泌蛋白前催乳素在通过内质网膜转运过程中被捕获时的蛋白质环境。将单个光反应基团置于不同长度的新生多肽链的不同位置，这些位置对应于转运过程的不同阶段，然后对与膜蛋白的光交联进行了分析。在所有情况下，发现从核糖体延伸出的多肽片段位于一种几乎完全由Sec61α形成的膜环境中，Sec61α是Sec61p复合物的多次跨膜亚基，对易位至关重要。在易位过程的早期阶段，在信号序列切割之前，几乎整个从核糖体出来的新生链都与Sec61α接触。“易位链相关膜”蛋白主要与信号序列在其疏水核心之前的区域相互作用。我们的研究结果表明，新生链直接从核糖体转移到一个蛋白质传导通道中，该通道的主要成分是Sec61α。
We have extended a previously developed photocrosslinking approach to systematically probe the protein environment of the secretory protein preprolactin, trapped during its transfer through the endoplasmic reticulum membrane. Single photoreactive groups were placed at various positions of nascent polypeptide chains of various length, corresponding to different stages of the transport process, and photo-crosslinks to membrane proteins were analyzed. In all cases, the polypeptide segment extending from the ribosome was found to be located in a membrane environment that is formed almost exclusively from Sec61 alpha, the multi-spanning subunit of the Sec61p complex that is essential for translocation. At early stages of the translocation process, before cleavage of the signal sequence, almost the entire nascent chain emerged from the ribosome contacts Sec61 alpha. The 'translocating chain-associating membrane' protein interacts mainly with the region of the signal sequence preceding its hydrophobic core. Our results suggest that the nascent chain is transferred directly from the ribosome into a protein-conducting channel, the major constituent of which is Sec61 alpha.