A class of membrane proteins with a C-terminal anchor
A class of membrane proteins with a C-terminal anchor
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DOI：
10.1016/0962-8924(93)90066-a
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发表时间：
1993-01-01
影响因子：
19
通讯作者：
Rapoport, Tom A.
中科院分区：
文献类型：
--
作者：
Kutay, Ulrike;Hartmann, Enno;Rapoport, Tom A.
蛋白质插入膜和完全跨膜转运的过程似乎在机制上是相似的。例如，ER膜蛋白和分泌蛋白都具有相似的疏水性信号序列，这些序列在多肽延伸过程中被信号识别颗粒（SRP）识别（参见参考文献1的综述）。新生链必须在N.从核糖体出现的末端信号序列变得可接近SRP 2。在多肽穿过内质网膜的转运过程中，开始于核糖体结合的新生链和SRP的复合物对接到膜上，膜和分泌蛋白共同的其他转运组分似乎也参与其中（参见参考文献1）。然而，有可能膜蛋白需要额外的组件来插入，例如终止转移序列3的受体。穿过或插入内膜的线粒体蛋白质也共享易位组分（参见参考文献4的综述）。此外，至少有一些线粒体外膜的蛋白质似乎有信号在其N-末端类似于那些目标其他蛋白质的矩阵S。相比之下，一类完整的膜蛋白，有他们的膜锚在C-末端似乎不遵循这些一般规则。该类的原型成员是细胞色素b的ER-形式，长期以来一直注意到其行为异常6-8。它在细胞质中定向并通过疏水C末端序列锚定在膜中，该疏水C末端序列被称为“插入序列”以将其与信号序列9区分开。尽管在结构
The processes of protein insertion into membranes and complete translocation across membranes seem to be mechanistically similar. For example, both ER membrane proteins and secretory proteins have similar hydrophobic signal sequences that are recognized by the signal recognition particle (SRP) during polypepttde elongation (see Ref. 1 for a review). The nascent chains must be at] east 60 amino acid residues long before the N. terminal signal sequence emerging from the ribosome becomes accessible to the SRP 2. During the translocation of a polypepqde across the ER membrane, which begins after docking of the complex of ribosome-bound nascent chain and SRP onto the membrane, other translocation components common to both membrane and secretory proteins seem to be involved (see Ref. 1 for a review). However, it is possible that membrane proteins require additional components for their insertion, such as receptors for stop-transfer sequences 3. Mitochondrial proteins transported across or inserted into the inner membrane also share translocation components (see Ref. 4 for a review). In addition, at least some proteins of the outer mitochondrial membrane appear to have signals at their N-termini similar to those that target other proteins to the matrix s.By contrast, a class of integral membrane proteins that have their membrane anchors at the C-terminus does not seem to follow these general rules. The archetype member of this class is the ER-form of cytochrome bs, which has long been noted to be exceptional in its behaviour 6-8. It is cytoplasmically oriented and anchored in the membrane by a hydrophobic C-terminal sequence that has been called an'insertion sequence'to distinguish it from a signal sequence 9. Although structurally