Bird P, Gething M J, Sambrook J
Department of Biochemistry, University of Texas Health Center, Dallas 75235.
J Cell Biol. 1987 Dec;105(6 Pt 2):2905-14. doi: 10.1083/jcb.105.6.2905.
In Saccharomyces cerevisiae, nascent carboxypeptidase Y (CPY) is directed into the endoplasmic reticulum by an NH2-terminal signal peptide that is removed before the glycosylated protein is transported to the vacuole. In this paper, we show that this signal peptide does not function in mammalian cells: CPY expressed in COS-1 cells is not glycosylated, does not associate with membranes, and retains its signal peptide. In a mammalian cell-free protein-synthesizing system, CPY is not translocated into microsomes. However, if the CPY signal is either mutated to increase its hydrophobicity or replaced with that of influenza virus hemagglutinin, the resulting precursors are efficiently translocated both in vivo and in vitro. The implications of these results for models of signal sequence function are discussed.
在酿酒酵母中，新生的羧肽酶Y（CPY）通过氨基末端信号肽被引导进入内质网，该信号肽在糖基化蛋白被转运到液泡之前被切除。在本文中，我们表明该信号肽在哺乳动物细胞中不起作用：在COS-1细胞中表达的CPY未被糖基化，不与膜结合，并保留其信号肽。在无细胞的哺乳动物蛋白质合成系统中，CPY不会转运到微粒体中。然而，如果CPY信号发生突变以增加其疏水性，或者被流感病毒血凝素的信号肽取代，则产生的前体在体内和体外都能有效地转运。本文讨论了这些结果对信号序列功能模型的影响。
