The genetic code in bovine mitochondria: sequence of genes for the cytochrome oxidase subunit II and two tRNAs

Bovine-heart mitochondrial DNA from a single animal was isolated and fragments representative of the entire genome cloned into multicopy plasmid vectors to facilitate determination of its complete nucleotide sequence. We present here the sequence of the region covering the gene for cytochrome oxidase subunit II. Comparison of this sequence with the amino acid sequence of the homologous beef-heart protein has enabled the determination of most of the bovine mitochondrial genetic code. The code differs from the “universal” genetic code in that UGA codes for tryptophan and not termination, and AUA codes for methionine and not isoleucine. The only codon family not represented is the AGA/AGG pair normally used for arginine; evidence from other genes suggests that these code for termination in bovine mitochondria. The sequence presented also includes the adjacent tRNA^Asp and tRNA^Lys genes. The tRNA^Asp gene is separated by one nucleotide from the 5' end of the COII gene and only three bases separate the 3' end of this gene and the adjacent tRNA^Lys gene. This highly compact gene organisation is very similar to that found in the corresponding region of the human mitochondrial genome and the gene arrangement is identical. The structures of the respective bovine and human tRNAs vary primarily in the “D-” and “TΨC-loops”.