The hydrophobic core of the Sec61 translocon defines the hydrophobicity threshold for membrane integration.
The hydrophobic core of the Sec61 translocon defines the hydrophobicity threshold for membrane integration.
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DOI：
10.1091/mbc.e10-01-0060
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发表时间：
2010-05-15
影响因子：
3.3
通讯作者：
Spiess M
中科院分区：
文献类型：
--
作者：
Junne T;Kocik L;Spiess M
突变的非极性收缩的酵母Sec61易位到极性或带电残基，同时保留功能，影响潜在的跨膜段到脂质双层的整合。这表明，在设置膜整合的疏水性阈值的易位发挥了积极的作用。Sec61易位子介导蛋白质跨内质网膜的易位和跨膜片段横向整合到脂质双层中。闲置的易位子的结构是封闭的内腔塞域和疏水收缩环。为了测试非极性收缩的功能，我们将酵母Sec61p的所有六个环残基突变为更亲水、体积更大或甚至带电荷的氨基酸（丙氨酸、甘氨酸、丝氨酸、色氨酸、赖氨酸或精氨酸）。发现易位子甚至对收缩环中的电荷突变具有令人惊讶的耐受性，因为生长和易位效率没有受到显著影响。最有趣的是，环突变体被发现会影响疏水序列整合到脂质双层中，这表明易位子并不简单地催化水环境和脂质双层之间潜在的跨膜区段的分配，但它也在设置膜整合的疏水性阈值中起着积极的作用。
Mutation of the apolar constriction of the yeast Sec61 translocon to polar or charged residues, while retaining functionality, affected the integration of potential transmembrane segments into the lipid bilayer. This indicates that the translocon plays an active role in setting the hydrophobicity threshold for membrane integration. The Sec61 translocon mediates the translocation of proteins across the endoplasmic reticulum membrane and the lateral integration of transmembrane segments into the lipid bilayer. The structure of the idle translocon is closed by a lumenal plug domain and a hydrophobic constriction ring. To test the function of the apolar constriction, we have mutated all six ring residues of yeast Sec61p to more hydrophilic, bulky, or even charged amino acids (alanines, glycines, serines, tryptophans, lysines, or aspartates). The translocon was found to be surprisingly tolerant even to the charge mutations in the constriction ring, because growth and translocation efficiency were not drastically affected. Most interestingly, ring mutants were found to affect the integration of hydrophobic sequences into the lipid bilayer, indicating that the translocon does not simply catalyze the partitioning of potential transmembrane segments between an aqueous environment and the lipid bilayer but that it also plays an active role in setting the hydrophobicity threshold for membrane integration.
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