Studies on the biosynthesis of microsomal membrane proteins. Site of synthesis and mode of insertion of cytochrome b5, cytochrome b5 reductase, cytochrome P-450 reductase and epoxide hydrolase.
Studies on the biosynthesis of microsomal membrane proteins. Site of synthesis and mode of insertion of cytochrome b5, cytochrome b5 reductase, cytochrome P-450 reductase and epoxide hydrolase.
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微粒体膜蛋白生物合成的研究。
DOI：
10.1111/j.1432-1033.1982.tb05894.x
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发表时间：
1982
期刊：
影响因子：
--
通讯作者：
Kreibich,G
中科院分区：
文献类型：
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作者：
Okada,Y;Frey,AB;Guenthner,TM;Oesch,F;Sabatini,DD;Kreibich,G
使用体外编程的翻译系统，使用多聚核糖体或从游离和膜结合大鼠肝多聚核糖体中提取的mRNA，研究了几种微粒体多肽的合成位点和插入膜的机制。通过特异性免疫沉淀分离细胞色素B5的初级翻译产物，NADH：细胞色素B5氧化还原酶，NADPH：细胞色素P-450氧化还原酶和环氧化物水解酶，并与成熟蛋白进行比较。进行了以下观察：1细胞色素b 5和NADH：细胞色素b 5氧化还原酶在游离多聚体中合成，NADPH：细胞色素P-450氧化还原酶和环氧化物水解酶在膜结合多聚体中合成。2在所有情况下，体外合成的放射性标记产物与纯化的天然多肽一起迁移。由于这些蛋白质不是糖蛋白，因此可以推断，在体内，它们在分解期间或之后不经历蛋白水解切割。3编码NADPH的可翻译mRNA的水平：细胞色素P-450氧化还原酶或环氧化物水解酶分别被苯巴比妥或各种致癌物增加。4天然环氧化物水解酶和体外合成的环氧化物水解酶的氨基末端片段的比较表明，这种蛋白质保留了氨基末端类似于分泌前蛋白中发现的瞬时插入信号的多肽序列。5 NADPH的氨基末端区域：细胞色素P-450氧化还原酶在其前15个氨基酸中含有7个亮氨酸残基，因此，推测是将该多肽锚定到膜上的疏水部分。可以解释膜蛋白的空间分布及其内质网膜的选择性积累进行了讨论。
The site of synthesis and mechanism of insertion into membranes of several microsomal polypeptides was studied using translation system programmedin vitrowith polysomes or with mRNA extracted from free and membrane‐bound rat liver polysomes. Primary translation products of cytochromeb5, NADH: cytochromeb5oxidoreductase, NADPH: cytochrome P‐450 oxidoreductase and epoxide hydrolase were isolated by specific immunoprecipitation and compared with the mature proteins. The following observations were made:1While cytochromeb5and NADH: cytochromeb5oxidoreductase are synthesized in free polysomes, NADPH: cytochrome P‐450 oxidoreductase and epoxide hydrolase are made in membrane‐bound polysomes.2In all cases the radioactively labelled products synthesizedin vitrocomigrated with the purified native polypeptides. Since these proteins are not glycoproteins, it can be inferred thatin vivothey do not undergo proteolytic cleavage during or after translation.3Levels of translatable mRNA coding for NADPH: cytochrome P‐450 oxidoreductase or epoxide hydrolase were increased by phenobarbital or by various carcinogens respectively.4A comparison of amino‐terminal segments of the native epoxide hydrolase and that synthesizedin vitroshowed that this protein retains an amino‐terminal polypeptide sequence which resembles the transient insertion signal found in presecretory proteins.5The amino‐terminal region of NADPH: cytochrome P‐450 oxidoreductase contains 7 leucine residues in its first 15 amino acids and can, therefore, be presumed to be the hydrophobic portion which anchors this poly‐ peptide to the membrane.Mechanisms which may account for the spatial disposition of the membrane proteins and for their selective accumulation in endoplasmic reticulum membranes are discussed.