A second trimeric complex containing homologs of the Sec6lp complex functions in protein transport across the ER membrane of S-cerevisiae
A second trimeric complex containing homologs of the Sec6lp complex functions in protein transport across the ER membrane of S-cerevisiae
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DOI：
10.1002/j.1460-2075.1996.tb00492.x
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发表时间：
1996-04-01
期刊：
影响因子：
11.4
通讯作者：
Sommer, T
中科院分区：
文献类型：
--
作者：
Finke, K;Plath, K;Sommer, T
酵母微粒体含有七聚体Sec复合物，参与翻译后的蛋白质运输，该复合物由异三聚体Sec61p复合物和四聚体Sec62-Sec63p复合物组成，三聚体Sec61p复合物也作为一个独立的实体存在，可能在共翻译蛋白质运输中起作用，就像它在哺乳动物中的同源物一样。我们现在在酵母内质网膜中发现了第二种结构相关的三聚体复合物，称为Ssh1p复合物。它由Sec61p的远亲Ssh1p （sec61同源物1）、Sec61p复合物的sh1p亚基的同源物sh2p和Sss1p组成，Sss1p是这两种三聚体复合物的共同成分。与Sec61p相反，Ssh1p不是细胞活力所必需的，但它是正常生长速率所必需的，sh1p和sh2p单独也不是必需的。但缺乏这两种蛋白质的细胞在高温下生长受损，并积累分泌蛋白的前体；从这些细胞中分离出的微粒体也表现出翻译后蛋白质转运率的降低。与Sec61p复合体一样，Ssh1p复合体与膜结合核糖体相互作用，但它不与Sec62-Sec63p复合体结合形成七聚体Sec复合体，因此我们认为它只在蛋白质运输的共翻译途径中起作用。
Yeast microsomes contain a heptameric Sec complex involved in post-translational protein transport that is composed of a heterotrimeric Sec61p complex and a tetrameric Sec62-Sec63p complex, The trimeric Sec61p complex also exists as a separate entity that probably functions in co-translational protein transport, like its homolog in mammals, We have now discovered in the yeast endoplasmic reticulum membrane a second, structurally related trimeric complex, named Ssh1p complex, It consists of Ssh1p (Sec Sixty-one homolog 1), a rather distant relative of Sec61p, of Sbh2p, a homolog of the Sbh1p subunit of the Sec61p complex, and of Sss1p, a component common to both trimeric complexes, In contrast to Sec61p, Ssh1p is not essential for cell viability but it is required for normal growth rates, Sbh1p and Sbh2p individually are also not essential, but cells lacking both proteins are impaired in their growth at elevated temperatures and accumulate precursors of secretory proteins; microsomes isolated from these cells also exhibit a reduced rate of posttranslational protein transport. Like the Sec61p complex, the Ssh1p complex interacts with membrane-bound ribosomes, but it does not associate with the Sec62-Sec63p complex to form a heptameric Sec complex, We therefore propose that it functions exclusively in the co-translational pathway of protein transport.