SEC62 encodes a putative membrane protein required for protein translocation into the yeast endoplasmic reticulum.
SEC62 encodes a putative membrane protein required for protein translocation into the yeast endoplasmic reticulum.
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DOI：
10.1083/jcb.109.6.2653
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发表时间：
1989-12
期刊：
影响因子：
--
通讯作者：
Schekman R
中科院分区：
文献类型：
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作者：
Deshaies RJ;Schekman R
酵母sec 62突变体细胞在将几种分泌前体蛋白易位到内质网腔中方面有缺陷（Rothblatt等人，1989年）。缺陷，这是最具限制性的α-因子前体（PP α F）和preprocarboxypeptidase Y，已在体外重现。从突变体细胞分离的膜显示低的和不稳定的易位活性，其中pp α F在野生型胞质溶胶部分中翻译。该缺陷是膜组分所特有的，因为来自突变细胞的胞质溶胶支持从野生型酵母易位到膜中。转化酶组装在体内仅部分受sec 62突变的影响，并且在体外与突变膜几乎正常。SEC 62基因产物的潜在膜定位得到分子克隆评价的支持。DNA序列分析表明，一个32 kD的蛋白质没有明显的NH 2-末端信号序列，但有两个域的足够的长度和疏水性跨越脂质双层。Sec 62 p被预测在ER膜的细胞质表面上显示显著的NH 2-和COOH-末端亲水结构域。COOH末端的最后30个氨基酸可以形成α-螺旋，其中14个赖氨酸和精氨酸残基均匀地排列在螺旋周围。该结构域可能允许Sec 62 p与推定的易位复合物的其他蛋白质相互作用。
Yeast sec62 mutant cells are defective in the translocation of several secretory precursor proteins into the lumen of the endoplasmic reticulum (Rothblatt et al., 1989). The deficiency, which is most restrictive for alpha-factor precursor (pp alpha F) and preprocarboxypeptidase Y, has been reproduced in vitro. Membranes isolated from mutant cells display low and labile translocation activity with pp alpha F translated in a wild-type cytosol fraction. The defect is unique to the membrane fraction because cytosol from mutant cells supports translocation into membranes from wild-type yeast. Invertase assembly is only partly affected by the sec62 mutation in vivo and is nearly normal with mutant membranes in vitro. A potential membrane location for the SEC62 gene product is supported by evaluation of the molecular clone. DNA sequence analysis reveals a 32- kD protein with no obvious NH2-terminal signal sequence but with two domains of sufficient length and hydrophobicity to span a lipid bilayer. Sec62p is predicted to display significant NH2- and COOH- terminal hydrophilic domains on the cytoplasmic surface of the ER membrane. The last 30 amino acids of the COOH terminus may form an alpha-helix with 14 lysine and arginine residues arranged uniformly about the helix. This domain may allow Sec62p to interact with other proteins of the putative translocation complex.