Collins R A, Bertrand H, LaPolla R J, Lambowitz A M
Mol Gen Genet. 1981;181(1):13-9. doi: 10.1007/BF00338998.
[C93] is a novel, extranuclear mutant of Neurospora crassa which has a normal mitochondrial phenotype when grown at 25 degrees, but which is deficient in cytochromes b and aa3 when grown at 37 degrees (Pittenger and West 1979). In the present work, the phenotype of [C93] was characterized in greater detail. When [C93] is grown at 37 degrees, the rate of mitochondrial protein synthesis is decreased to approximately 25% that of wild type; the ratio of mitochondrial small to large ribosomal subunits is decreased to 1:4 and mitochondrial small subunits are deficient in the mitochondrially-synthesized protein, S-5. The mitochondrial ribosome assembly defects in 37 degrees-grown [C93] resemble those in chloramphenicol-treated wild-type cells and could merely be a consequence of the decreased rate of mitochondrial protein synthesis. Analysis of mitochondrial translation products by SDS gel electrophoresis suggests that 37 degrees-grown [C93] is grossly deficient in the 19,000 Mr subunit of the oligomycin-sensitive ATPase relative to other mitochondrially-synthesized proteins. The ATPase defect was not found in other extranuclear or nuclear mutants deficient in mitochondrial protein synthesis. These data and additional evidence suggest that the primary defect in [C93] may be in the assembly of the ATPase complex. The possible connection between the ATPase defect and the deficiency of mitochondrial protein synthesis is discussed.
[C93]是粗糙脉孢菌的一种新型核外突变体，在25摄氏度下生长时具有正常的线粒体表型，但在37摄氏度下生长时细胞色素b和aa3缺乏（皮滕杰和韦斯特，1979年）。在本研究中，对[C93]的表型进行了更详细的表征。当[C93]在37摄氏度下生长时，线粒体蛋白质合成速率降至野生型的约25%；线粒体小核糖体亚基与大核糖体亚基的比例降至1:4，线粒体小亚基缺乏线粒体合成的蛋白质S-5。在37摄氏度下生长的[C93]中的线粒体核糖体组装缺陷类似于氯霉素处理的野生型细胞中的缺陷，可能仅仅是线粒体蛋白质合成速率降低的结果。通过SDS凝胶电泳分析线粒体翻译产物表明，相对于其他线粒体合成的蛋白质，在37摄氏度下生长的[C93]中寡霉素敏感ATP酶的19,000 Mr亚基严重缺乏。在其他线粒体蛋白质合成缺陷的核外或核突变体中未发现ATP酶缺陷。这些数据和其他证据表明，[C93]中的主要缺陷可能在于ATP酶复合物的组装。讨论了ATP酶缺陷与线粒体蛋白质合成缺陷之间的可能联系。
