Rapid evolution of the human gene for cytochrome c oxidase subunit IV.

We have compared the DNA sequences of nine mammalian genes for cytochrome c oxidase subunit IV (COX4 genes)--four expressed genes (human, bovine, rat, and mouse) and five pseudogenes (human, chimpanzee, orangutan, squirrel monkey, and bovine)--and constructed the sequence of the ancestral mammalian COX4 gene. By analyzing these sequences to determine the pattern and rate of nucleotide substitution in each branch of the evolutionary tree, we deduced that the human gene has evolved rapidly since the origin of the primate pseudogene approximately 41 million years ago, and we discuss the suggestion that this results from coevolution of nuclear and mitochondrial genes for cytochrome c oxidase.