A cDNA encoding subunit Va of cytochrome c oxidase (EC 1.9.3.1) was cloned and characterized from a lesser grain borer (Rhyzopertha dominica) cDNA library. The complete cDNA consists of 693-bp and contains an open reading frame of 450-bp that encodes 150 amino acid residues. The sequence includes a 28-bp putative N-terminal and a 122-bp putative mature protein. The estimated molecular weight and pI for the predicted mature protein are 13,962 and 4.60, respectively. The cDNA-deduced amino acid sequence of the mature protein shows 73% identity to that of a corresponding subunit of African malaria mosquito (Anopheles gambiae) and 59% identity to that of the fruit fly (Drosophila melanogaster). In addition, 31% of all amino acid residues are conserved among six different animal species. Evolutionary distance analysis suggests that cytochrome c oxidase subunit Va from R. dominica is most similar to the corresponding subunit from the malaria mosquito. Northern analysis revealed a single 4.9-kb transcript that is much larger than that found in mammalian species.