  The proper functioning of mitochondria requires that both the mitochondrial
and the nuclear genome are functional. To investigate the importance of the
mitochondrial genome, which encodes only 13 subunits of the respiratory
complexes, the mitochondrial rRNAs and a few tRNAs, we performed a comparative
study on the 143B cell line and on its Rho-0 counterpart, i.e., devoid of
mitochondrial DNA. Quantitative differences were found, of course in the
respiratory complexes subunits, but also in the mitochondrial translation
apparatus, mainly mitochondrial ribosomal proteins, and in the ion and protein
import system, i.e., including membrane proteins. Various mitochondrial
metabolic processes were also altered, especially electron transfer proteins
and some dehydrogenases, but quite often on a few proteins for each pathway.
This study also showed variations in some hypothetical or poorly characterized
proteins, suggesting a mitochondrial localization for these proteins. Examples
include a stomatin-like protein and a protein sharing homologies with bacterial
proteins implicated in tyrosine catabolism. Proteins involved in apoptosis
control are also found modulated in Rho-0 mitochondria.
