Protein translocation across the endoplasmic reticulum membrane: identification by photocross-linking of a 39-kD integral membrane glycoprotein as part of a putative translocation tunnel.
Protein translocation across the endoplasmic reticulum membrane: identification by photocross-linking of a 39-kD integral membrane glycoprotein as part of a putative translocation tunnel.
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DOI：
10.1083/jcb.109.5.2033
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发表时间：
1989-11
期刊：
影响因子：
--
通讯作者：
Walter P
中科院分区：
文献类型：
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作者：
Krieg UC;Johnson AE;Walter P
通过光交联检查分泌蛋白在跨ER膜转运期间的分子环境。新生的各种长度的催乳素前体链，合成截短的信使RNA在体外翻译的N-（5-叠氮基-2-硝基苯甲酰基）-Lys-tRNA的存在下，信号识别颗粒，和微粒体膜，被用来定位在膜内的不同位置的光反应性探针。光解后，每个新生链物种交联的一个完整的膜糖蛋白与推导的质量为39 kD（mp39）通过位于信号序列或成熟的催乳素序列的光反应性赖氨酸。因此，不同部分的新生催乳素前体链是在紧密接近相同的膜蛋白在易位过程中，和mp39因此似乎是一部分的易位子，蛋白质易位的特定网站的ER膜。mp39和先前鉴定为信号序列受体的糖蛋白的分子和交联性质的相似性（Wiedmann，M.，T. V. Kurzchalia，E. Hartmann和T. A.拉波波特1987.自然[伦敦]。328：830-833）表明这两种蛋白质可能是相同的。然而，我们的数据表明，mp39不（或不仅）作为一个信号序列受体的功能，而是可能是一个假定的易位隧道的一部分。
The molecular environment of secretory proteins during translocation across the ER membrane was examined by photocross-linking. Nascent preprolactin chains of various lengths, synthesized by in vitro translation of truncated messenger RNAs in the presence of N epsilon-(5- azido-2-nitrobenzoyl)-Lys-tRNA, signal recognition particle, and microsomal membranes, were used to position photoreactive probes at various locations within the membrane. Upon photolysis, each nascent chain species was cross-linked to an integral membrane glycoprotein with a deduced mass of 39 kD (mp39) via photoreactive lysines located in either the signal sequence or the mature prolactin sequence. Thus, different portions of the nascent preprolactin chain are in close proximity to the same membrane protein during the course of translocation, and mp39 therefore appears to be part of the translocon, the specific site of protein translocation across the ER membrane. The similarity of the molecular and cross-linking properties of mp39 and the glyco-protein previously identified as a signal sequence receptor (Wiedmann, M., T. V. Kurzchalia, E. Hartmann, and T. A. Rapoport. 1987. Nature [Lond.]. 328: 830-833) suggests that these two proteins may be identical. Our data indicate, however, that mp39 does not (or not only) function as a signal sequence receptor, but rather may be part of a putative translocation tunnel.