Chuck S L, Lingappa V R
Department of Microbiology and Immunology, University of California, San Francisco 94143-0444.
Cell. 1992 Jan 10;68(1):9-21. doi: 10.1016/0092-8674(92)90202-n.
Previously, we described the stepwise translocation of a large amino-terminal fragment of apolipoprotein B (apo B15) in which the nascent secretory chain translocates through a series of distinct, nonintegrated transmembrane intermediates with large domains exposed to the cytoplasm. Thus, apo B15 appears to stop and restart translocation at several points. We have identified a sequence of amino acids in apo B15 that confers this behavior on a heterologous chimeric protein. In addition, we dissect pausing into two distinct steps, stopping and restarting, thereby trapping otherwise transient intermediates. Finally, we demonstrate the function of a second "pause transfer" sequence over 200 amino acids downstream in apo B15 that restarts translocation posttranslationally, suggesting that multiple pause transfer sequences are involved in the biogenesis of apolipoprotein B.
此前，我们描述了载脂蛋白B（apo B15）一个大的氨基末端片段的逐步转运过程，其中新生分泌链通过一系列不同的、非整合的跨膜中间体进行转运，这些中间体有大的结构域暴露于细胞质中。因此，apo B15似乎在几个点上停止并重新开始转运。我们已经在apo B15中鉴定出一段氨基酸序列，该序列赋予异源嵌合蛋白这种行为。此外，我们将暂停分为两个不同的步骤，即停止和重新开始，从而捕获原本短暂的中间体。最后，我们证明了apo B15下游超过200个氨基酸处的第二个“暂停转移”序列的功能，该序列在翻译后重新启动转运，这表明多个暂停转移序列参与了载脂蛋白B的生物合成。
