Actively transcribed and expressed gene in mussels.

Background: Animal mitochondrial genomes typically encode 37 genes: 13 proteins, 22 tRNAs and two rRNAs. However, many species represent exceptions to that rule. Bivalvia along with Nematoda and Platyhelminthes are often suspected to fully or partially lack the ATP synthase subunit 8 () gene. This raises the question as to whether they are really lacking this gene or is this maybe an annotation problem? Among bivalves, has been inferred to lack an ATP8 gene since the characterization of its mitochondrial genome in 1992 Even though recent bioinformatic analyses suggested that is present in spp., due to high divergence in predicted amino acid sequences, the existence of a functional gene in this group remains controversial.

Results: Here we demonstrate that mitochondrial open reading frames suggested to be (in male and female mtDNAs) are actively translated proteins We also provide evidence that both proteins are an integral part of the ATP synthase complex based on in-gel detection of ATP synthase activity and two-dimensional Blue-Native and SDS polyacrylamide electrophoresis.

Conclusion: Many organisms (e.g., Bivalvia along with Nematoda and Platyhelminthes) are considered to be lacking certain mitochondrial genes often only based on poor similarity between protein coding gene sequences in genetically closed species. In some situations, this may lead to the inference that the ATP8 gene is absent, when it is in fact present, but highly divergent. This shows how important complementary role protein-based approaches, such as those in the present study, can provide to bioinformatic, genomic studies (i.e., ability to confirm the presence of a gene).