Translocation of proteins across the endoplasmic reticulum. I. Signal recognition protein (SRP) binds to in-vitro-assembled polysomes synthesizing secretory protein.
Translocation of proteins across the endoplasmic reticulum. I. Signal recognition protein (SRP) binds to in-vitro-assembled polysomes synthesizing secretory protein.
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DOI：
10.1083/jcb.91.2.545
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发表时间：
1981-11
期刊：
影响因子：
--
通讯作者：
Blobel G
中科院分区：
文献类型：
--
作者：
Walter P;Ibrahimi I;Blobel G
由六条多肽链组成的11 S蛋白质先前从狗胰腺微粒体膜的盐提取物中纯化，并且显示出是新生分泌蛋白质穿过微粒体膜易位所需的（Wistar和Blobel 1980 Proc.Natl. Acad. Sci.联合S. A. 77：7112-7116）。该11 S蛋白，称为信号识别蛋白（SRP），已在此显示（a）在小麦胚芽无细胞系统中选择性地抑制mRNA翻译为分泌蛋白（牛前催乳素），但不包括细胞质蛋白的mRNA（兔珠蛋白的α和β链）;（B）以相对低的亲和力结合（表观KD小于5 × 10 ~（-5））;和（c）选择性地与6结合，000倍高亲和力（表观KD小于8 × 10 ~（-9））与小麦胚中参与分泌蛋白合成的核糖体结合，而与参与胞质蛋白合成的核糖体结合不明显。N-乙基马来酰亚胺修饰后，SRP的低亲和力和高亲和力结合以及选择性抑制作用均被消除。当亮氨酸（Leu）类似物β-羟基亮氨酸掺入新生分泌多肽中时，SRP的高亲和力结合和选择性抑制作用在很大程度上被消除。
An 11S protein composed of six polypeptide chains was previously purified from a salt extract of dog pancreas microsomal membranes and shown to be required for translocation of nascent secretory protein across the microsomal membrane (Wistar and Blobel 1980 Proc. Natl. Acad. Sci. U. S. A. 77:7112-7116). This 11S protein, termed signal recognition protein (SRP), has been shown here (a) to inhibit translation in the wheat germ cell-free system selectively of mRNA for secretory protein (bovine preprolactin) but not of mRNA for cytoplasmic protein (alpha and beta chain of rabbit globin); (b) to bind with relatively low affinity (apparent KD less than 5 x 10(-5)) to monomeric wheat germ ribosomes; and (c) to bind selectively and with 6,000-fold higher affinity (apparent KD less than 8 x 10(-9)) to wheat germ ribosomes engaged in the synthesis of secretory protein but not to those engaged in the synthesis of cytoplasmic protein. Low- and high- affinity binding as well as the selective translation-inhibitory effect were abolished after modification of SRP by N-ethyl maleimide. High- affinity binding and the selective translation-inhibitory effect of SRP were largely abolished when the leucine (Leu) analogue beta-hydroxy leucine was incorporated into the nascent secretory polypeptide.