The turnover of the protein components of the inner and outer membrane fractions of rat liver mitochondria.

The mechanism of mitochondrial turnover and its relationship to the process of mitochondrial biogenesis is still uncertain. Fletcher and Sanadi (1961) reported that several protein components and lipids of rat liver mitochondria had an identical turnover rate. This suggested to these workers that liver mitochondria were labile and were broken down as an entity. Subsequent studies of Beattie, Basford, and Koritz (1967a) indicated that several mitochondrial protein subfractions had an essentially similar half-life, although the soluble proteins of kidney mitochondria had a more rapid turnover. In a recent study, Gross, Getz and Rabinowitz (19691, have also reported that rat liver mitochondrial DNA has a half-life of 9.4 days which is similar to that for the proteins previously published. The inner and outer mitochondrial membranes appear to have different routes of biosynthesis. Isolated mitochondria are capable of incorporating amino acids only into certain insoluble proteins of the inner membrane (Beattie, Basford and Koritz, 1967b). In