Fate of Cleaved Signal Peptides of the Endoplasmic Reticulum

蛋白质跨特定细胞内转运的机制 细胞膜是细胞生物学的核心问题。 该项目重点 在疏水信号序列上， 跨内质网（ER）膜的分泌蛋白， 这是细胞分泌蛋白质的第一步。 的 信号序列的重要性已经得到了很好的建立，但是它们的 一旦通过ER的作用从前体蛋白中去除， 膜蛋白信号肽酶，是未知的。 的目标 要进行的实验是研究蛋白水解 含有功能信号序列的不同多肽， 一项旨在确定一种建议的信号肽水解酶活性的努力， 非洲爪蟾卵母细胞。 这两种工程化的细胞内命运 和未修饰的裂解的信号肽， 将表征它们的降解特性。 结果 这些研究的一部分将用于开发一种工作测定法， 非洲爪蟾卵母细胞中信号肽水解酶。 这样的分析是 对于鉴定和纯化 特异性代谢切割信号序列。 这些蛋白质 可能不仅对于清除来自 细胞，但也在实际的易位机制， ER膜。 将采用的技术，以遵循 非洲爪蟾卵母细胞中裂解的信号肽的命运可能提供了一个 一个强大的工具，用于分解转移中的离散步骤 蛋白质穿过活细胞的内质网膜。 %%% 蛋白质在内质网膜上的转移 在真核细胞中合成是关键的第一步， 将蛋白质贩运到各种目的地，包括 溶酶体和细胞外空间（分泌）。 我们的进展 理解这一基本过程不仅重要， 对于细胞功能的一般理解， 生物技术. 这个项目解决的问题的命运， 切割的信号序列，也就是新的- 通过内质网运输所需的合成蛋白质 膜，但不是“成品”蛋白质产品的一部分 并因此从蛋白质的其余部分酶切 在转移完成后不久。 这是细胞的一个区域 生物学很少受到关注，尽管 关于分泌物的其他方面的研究活动水平 过程 有一个很好的可能性，不可预见的新的和 这项工作将产生潜在的重要见解。

The mechanism of protein transport across specific intracellular membranes is a central issue in cell biology. This project focuses on the hydrophobic signal sequences which direct the transfer of secretory proteins across the endoplasmic reticulum (ER) membrane, the first step in the secretion of proteins from the cell. The importance of signal sequences has been well-established, but their fate, once removed from precursor proteins by the action of the ER membrane protein signal peptidase, is unknown. The objective of the experiments to be carried out is to investigate the proteolysis of different polypeptides containing functional signal sequences in an effort to define a proposed signal peptide hydrolase activity in Xenopus laevis oocytes. The intracellular fates of both engineered and unmodified cleaved signal peptides will be observed, and the properties of their degradation will be characterized. The results of these investigations will be used to develop a working assay for signal peptide hydrolases in Xenopus oocytes. Such an assay is essential to efforts to identify and purify the proteins which specifically metabolize cleaved signal sequences. These proteins may be important not only for clearance of signal sequences from cells, but also in the actual mechanism of translocation across the ER membrane. The technique which will be employed to follow the fate of cleaved signal peptides in Xenopus oocytes may provide a powerful tool for the dissection of discrete steps in the transfer of proteins across the ER membrane in living cells. %%% The transfer of proteins across the ER membrane as they are synthesized in eukaryotic cells is a critical first step in the trafficking of proteins to a variety of destinations, including lysosomes and the extracellular space (secretion). Advances in our understanding of this fundamental process are important not only for general understanding of how cells function, but also for biotechnology. This project addresses the question of the fate of the cleaved signal sequence, that is, the piece of the newly- synthesized protein which is required for transport across the ER membrane, but which is not part of the "finished" protein product and is therefore enzymatically cleaved from the rest of the protein very soon after the transfer is effected. This is an area of cell biology which has received very little attention, despite the high level of research activity on other aspects of the secretory process. There is a good likelihood that unforeseen new and potentially important insights will emerge from the work.