Precursor Polypeptides to Structural Proteins of Visna Virus
Precursor Polypeptides to Structural Proteins of Visna Virus
复制标题
维斯纳病毒结构蛋白的前体多肽
作者：
R. Vigne;P. Filippi;G. Quérat;N. Sauze;C. Vitu;P. Russo;P. Delori
维斯纳病毒是一种逆转录病毒，通过裂解循环在绵羊脉络丛的成纤维细胞样细胞中复制。Visna病毒体含有三种主要的低分子量蛋白质（p30、p16和p14），它们与基因组RNA和几种逆转录酶分子一起构成病毒体的核心结构。核心被含有主要糖蛋白（gp 135）的包膜包围。通过与肿瘤病毒类比，这三组结构蛋白（即，内部蛋白质、包膜糖蛋白和逆转录酶）可能分别由gag、env和pol基因编码。为了阐明维斯纳病毒基因组的遗传组织及其表达，我们研究了感染绵羊脉络丛细胞中病毒蛋白的合成。细胞内的病毒蛋白进行了检测，通过免疫沉淀的脉冲标记的细胞提取物与单特异性血清提出对p30，p16，和gp 135和分辨率的蛋白质的十二烷基硫酸钠-聚丙烯酰胺凝胶电泳。用抗p30和抗p16血清进行免疫沉淀，可以鉴定55，000-道尔顿多肽前体的内部病毒体蛋白p30、p16和p14（Pr 55 gag）。胰蛋白酶肽图证实了Pr 55 gag与三种内部蛋白之间的同源性。此外，还检测到150，000道尔顿的gag相关多肽。这种多肽的丰度低于Pr 55 gag，可能是病毒逆转录酶（Pr 150 gag-pol）的前体。Pr 55 gag和Pr 150 gag-pol未被糖基化。与主要包膜蛋白gp 135相关的前体是平均分子量为150，000的糖基化多肽（gPr 150 env）。脉冲追踪实验表明，gPr 150 env成熟为糖蛋白gp 135细胞内，然而，gp 135从来没有占优势的细胞提取物。在2-脱氧-d-葡萄糖存在下积累的gPr 150 env的非糖基化形式表现为约100，000道尔顿的多肽。这些结果表明，visna病毒编码的最大的非糖基化env相关的前体中的所有逆转录病毒，因此可能含有最大的env基因。
Visna virus is a retrovirus which replicates in fibroblast-like cells of the sheep choroid plexus through a lytic cycle. Visna virions contain three major low-molecular-weight proteins (p30, p16, and p14) which, together with the genomic RNA and several molecules of reverse transcriptase, constitute the core structure of the virions. The core is surrounded by an envelope containing a major glycoprotein (gp135). By analogy with the oncoviruses, these three groups of structural proteins (i.e., the internal proteins, the envelope glycoprotein, and the reverse transcriptase) are probably encoded by the gag, env, and pol genes, respectively. To elucidate the genetic organization of the visna virus genome and its expression, we studied the synthesis of viral proteins in infected sheep choroid plexus cells. Intracellular viral proteins were detected by immunoprecipitation of pulse-labeled cell extracts with monospecific sera raised against p30, p16, and gp135 and resolution of the proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Immunoprecipitation with anti-p30 and anti-p16 sera allowed the characterization of the 55,000-dalton polypeptide precursor to internal virion proteins p30, p16, and p14 (Pr55gag). Tryptic peptide mapping confirmed the precursor-product relationship between Pr55gag and the three internal proteins. In addition, a gag-related polypeptide of 150,000 daltons was also detected. This polypeptide, which was less abundant than Pr55gag, is a likely precursor to the viral reverse transcriptase (Pr150gag-pol). Pr55gag and Pr150gag-pol are not glycosylated. The precursor related to major envelope protein gp135 is a glycosylated polypeptide with an average molecular weight of 150,000 (gPr150env). Pulse-chase experiments indicated that gPr150env matures into glycoprotein gp135 intracellularly; however, gp135 was never preponderant in cell extracts. The non-glycosylated from of gPr150env, which accumulated in the presence of 2-deoxy-d-glucose, appeared as a polypeptide of about 100,000 daltons. These results indicated that visna virus codes for the largest non-glycosylated env-related precursor among all of the retroviruses and therefore probably contains the largest env gene.