Bar-Nun S, Kreibich G, Adesnik M, Alterman L, Negishi M, Sabatini D D
Proc Natl Acad Sci U S A. 1980 Feb;77(2):965-9. doi: 10.1073/pnas.77.2.965.
Treatment of rats with phenobarbital leads to a substantial increase in levels of translatable liver cytochrome P-450 mRNA. This mRNA is primarily associated with ribosomes bound to endoplasmic reticulum membranes which in an in vitro system synthesized approximately 10 times more cytochrome P-450 than did free polysomes from the same animals. Cytochrome P-450 synthesized by rough microsomes in vitro appears to be directly inserted into the membranes because it was not released by a treatment with low detergent concentrations that released albumin and other microsomal content proteins. The amino-terminal amino acid sequence of cytochrome P-450 synthesized in an mRNA-dependent system resembles in hydrophobicity the signal segment of presecretory proteins and therefore may serve to insert the polypeptide into the membrane during synthesis. In contrast to the situation with secretory proteins and several other membrane proteins, however, the putative insertion signal of cytochrome P-450 is not removed by a membrane-associated peptidase and remains in the mature polypeptide.
用苯巴比妥处理大鼠会导致可翻译的肝细胞色素P - 450 mRNA水平大幅增加。这种mRNA主要与结合在内质网膜上的核糖体相关，在体外系统中，这些核糖体合成的细胞色素P - 450比来自相同动物的游离多核糖体多约10倍。体外由糙面微粒体合成的细胞色素P - 450似乎直接插入膜中，因为用低浓度去污剂处理时它不会被释放，而低浓度去污剂能释放白蛋白和其他微粒体内容物蛋白。在依赖mRNA的系统中合成的细胞色素P - 450的氨基末端氨基酸序列在疏水性上类似于分泌前蛋白质的信号片段，因此可能在合成过程中将多肽插入膜中。然而，与分泌蛋白和其他几种膜蛋白的情况不同，细胞色素P - 450的假定插入信号不会被膜相关肽酶去除，并保留在成熟多肽中。
