Yeast carboxypeptidase Y can be translocated and glycosylated without its amino-terminal signal sequence.
Yeast carboxypeptidase Y can be translocated and glycosylated without its amino-terminal signal sequence.
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DOI：
10.1083/jcb.104.5.1183
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发表时间：
1987-05
期刊：
影响因子：
--
通讯作者：
Stevens TH
中科院分区：
文献类型：
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作者：
Blachly-Dyson E;Stevens TH
我们已经构建了一系列的酵母液泡蛋白羧肽酶Y（CPY）的信号序列中的突变，并已使用脉冲追踪放射性标记和免疫沉淀检查这些突变的突变体CPY蛋白进入分泌途径的体内效应。我们发现，带负电荷的残基，天冬氨酸，到信号序列的疏水核心的引入信号序列的功能没有明显的影响。相反，信号序列内的内部框内缺失导致CPY作为未糖基化的前体合成。这些被缓慢且低效地转化为糖基化前体，所述糖基化前体与由野生型基因产生的糖基化形式不可区分。这些前体以PEP 4依赖的方式转化为活性CPY，表明它们正确地定位于液泡。令人惊讶的是，去除整个CPY信号序列的缺失突变具有类似的效果：未糖基化的前体在携带该突变基因的细胞中积累，并且超过10%的前体在转录后被糖基化。因此，CPY的氨基末端信号序列虽然对易位效率很重要，但对于该蛋白的易位不是绝对必需的。
We have constructed a series of mutations in the signal sequence of the yeast vacuolar protein carboxypeptidase Y (CPY), and have used pulse- chase radiolabeling and immunoprecipitation to examine the in vivo effects of these mutations on the entry of the mutant CPY proteins into the secretory pathway. We find that introduction of a negatively charged residue, aspartate, into the hydrophobic core of the signal sequence has no apparent effect on signal sequence function. In contrast, internal in-frame deletions within the signal sequence cause CPY to be synthesized as unglycosylated precursors. These are slowly and inefficiently converted to glycosylated precursors that are indistinguishable from the glycosylated forms produced from the wild- type gene. These precursors are converted to active CPY in a PEP4- dependent manner, indicating that they are correctly localized to the vacuole. Surprisingly, a deletion mutation that removes the entire CPY signal sequence has a similar effect: unglycosylated precursor accumulates in cells carrying this mutant gene, and greater than 10% of it is posttranslationally glycosylated. Thus, the amino-terminal signal sequence of CPY, while important for translocation efficiency, is not absolutely required for the translocation of this protein.