The mitochondrial genome contains 37 genes that encode 13 proteins, 22 tRNAs, and 2 rRNAs. The 13 mitochondrial gene-encoded proteins all instruct cells to produce protein subunits of the enzyme complexes of the oxidative phosphorylation system, which enables mitochondria to act as the powerhouses of our cells. Mitochondrial Gene Expression
Mitochondrial gene expression is similar to nuclear expression in several respects. Transcription is responsive to some of the same nutrients and hormones that affect nuclear transcription. Both genomes require binding proteins but it seems that each compartment has its preferred binding form. Unlike the nuclear genome, where each gene has its own promoter region, all of the genes in the mitochondrial genome have a common promoter found in the D-loop. In contrast to nuclear gene transcription and translation that involves both the nuclear and the cytoplasmic compartments, mitochondrial transcription and translation occur totally within the mitochondrial compartment. It is affected by a wide variety of nuclear-encoded transcription factors and nutrients.