Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia B3H 4H7, Canada. M.W.Gray@dal.ca
Complete sequences of numerous mitochondrial, many prokaryotic, and several nuclear genomes are now available. These data confirm that the mitochondrial genome originated from a eubacterial (specifically alpha-proteobacterial) ancestor but raise questions about the evolutionary antecedents of the mitochondrial proteome.