A gene for cytochrome c oxidase subunit II in duck mitochondrial DNA: structural features and sequence evolution

The gene encoding cytochrome c oxidase subunit II (COXII) was amplified by polymerase chain reaction (PCR) using mitochondrial DNAs (mtDNAs) isolated from two genera of domesticated ducks, Anas platyrhnchos and Cairina muschata, and their intergeneric and intrageneric hybrids as templates. Comparison of the nucleotide sequences from the two different duck lineages shows that they have approximately 91% homology. The nucleotide substitution pattern in the duck COXII gene reveals a high transition/transversion ratio (8.8:1.0) while 93.2% of the nucleotide substitutions are silent. The duck COXII, which uses GUG as the initiation codon, contains 228 amino acid residues. Comparison of the deduced COXII amino acid sequences in duck, chicken, Xenopus laevis, mouse, bovine and human reveals five highly conserved domains. The evolutionary conservation of the primary structure of COXII implies its functional importance.