Harkness T A, Nargang F E, van der Klei I, Neupert W, Lill R
Institut für Physiologische Chemie, Physikalische Biochemie und Zellbiologie, Universität München, Federal Republic of Germany.
J Cell Biol. 1994 Mar;124(5):637-48. doi: 10.1083/jcb.124.5.637.
The novel genetic method of "sheltered RIP" (repeat induced point mutation) was used to generate a Neurospora crassa mutant in which MOM19, a component of the protein import machinery of the mitochondrial outer membrane, can be depleted. Deficiency in MOM19 resulted in a severe growth defect, but the cells remained viable. The number of mitochondrial profiles was not grossly changed, but mutant mitochondria were highly deficient in cristae membranes, cytochromes, and protein synthesis activity. Protein import into isolated mutant mitochondria was decreased by factors of 6 to 30 for most proteins from all suborganellar compartments. Proteins like the ADP/ATP carrier, MOM19, and cytochrome c, whose import into wild-type mitochondria occurs independently of MOM19 became imported normally showing that the reduced import activities are solely caused by a lack of MOM19. Depletion of MOM19 reveals a close functional relationship between MOM19 and MOM22, since loss of MOM19 led to decreased levels of MOM22 and reduced protein import through MOM22. Furthermore, MOM72 does not function as a general backup receptor for MOM19 suggesting that these two proteins have distinct precursor specificities. These findings demonstrate that the import receptor MOM19 fulfills an important role in the biogenesis of mitochondria and that it is essential for the formation of mitochondria competent in respiration and phosphorylation.
采用“保护性重复诱导点突变”（RIP）这种新的遗传方法，生成了一种粗糙脉孢菌突变体，其中线粒体外膜蛋白质导入机制的一个组分MOM19可以被耗尽。MOM19的缺失导致严重的生长缺陷，但细胞仍可存活。线粒体轮廓的数量没有明显变化，但突变体线粒体的嵴膜、细胞色素和蛋白质合成活性严重不足。对于来自所有亚细胞器区室的大多数蛋白质，导入分离的突变体线粒体中的蛋白质减少了6至30倍。像ADP/ATP载体、MOM19和细胞色素c等蛋白质，其导入野生型线粒体的过程独立于MOM19，现在却能正常导入，这表明导入活性降低完全是由于缺乏MOM19所致。MOM19的耗尽揭示了MOM19与MOM22之间密切的功能关系，因为MOM19的缺失导致MOM22水平降低以及通过MOM22的蛋白质导入减少。此外，MOM72并不作为MOM19的通用备用受体起作用，这表明这两种蛋白质具有不同的前体特异性。这些发现表明，导入受体MOM19在线粒体生物发生中发挥着重要作用，并且对于形成具有呼吸和磷酸化能力的线粒体至关重要。
