Marlhens F, Nicole A, Sinet P M
Biochem Biophys Res Commun. 1985 May 31;129(1):300-5. doi: 10.1016/0006-291x(85)91437-8.
The activity of manganese superoxide dismutase (MnSOD) revealed by specific staining after gel electrophoresis of cell extracts, is decreased in human fibroblasts transformed by SV40. The decrease in enzyme activity is attributable to decreased amount of enzyme protein as determined by radial immunodiffusion. Total fibroblast RNAs were translated in the presence of (35S) methionine in a cell-free translation system and the neo synthesized proteins submitted to immunoprecipitation with an anti MnSOD antiserum. Gel electrophoresis of the immunoprecipitated material followed by fluorography shows that MnSOD is translated as a peptide which is 2000 daltons larger than the mature enzyme subunit. This precursor (pre-MnSOD) is processed in vitro to mature MnSOD by the action of an isolated mitochondrial preparation. Levels of translatable MnSOD mRNA in normal and SV 40 transformed cells were compared in terms of the radioactivities incorporated into pre MnSOD bands. The results indicate that the decreased amount of MnSOD in SV 40 transformed fibroblasts is due to a decreased level of translatable mRNA for MnSOD.
通过对细胞提取物进行凝胶电泳后特异性染色所显示的锰超氧化物歧化酶（MnSOD）活性，在经SV40转化的人成纤维细胞中降低。酶活性的降低归因于放射免疫扩散法测定的酶蛋白量减少。在无细胞翻译系统中，在（35S）甲硫氨酸存在的情况下翻译总成纤维细胞RNA，并将新合成的蛋白质用抗MnSOD抗血清进行免疫沉淀。对免疫沉淀物质进行凝胶电泳，然后进行荧光自显影，结果表明MnSOD是以一种比成熟酶亚基大2000道尔顿的肽形式翻译的。这种前体（前MnSOD）在体外通过分离的线粒体制剂的作用加工成成熟的MnSOD。根据掺入前MnSOD条带的放射性，比较了正常细胞和SV40转化细胞中可翻译的MnSOD mRNA水平。结果表明，SV40转化的成纤维细胞中MnSOD量的减少是由于MnSOD可翻译mRNA水平的降低。
