Characterization of ATP-binding Cassette Transporter Genes in Silkworm, Bombyx Mori

Background: ATP-binding cassette (ABC) transporters are transmembrane proteins that utilize the energy of adenosine triphosphate (ATP) binding and hydrolysis to transport various substrates across extra and intracellular membranes, including metabolic products, lipids and sterols, and drugs. They play important roles in various processes of life, especially in drug resistance, metabolism and development. Objective: Identify the ATP-binding cassette (ABC) transporter gene family and their members in the genome of silkworm, Bombyx mori. Method: Bioinformatics and phylogenetic analysis were used in the study. Results: We identified 47 ABC proteins in the silkworm genome, which possesses members of all current ABC subfamilies A to H. ABC proteins of silkworm were compared to those from worm, fruit fly and human. A high conservation of silkworm ABC transporters were observed for proteins involved in fundamental cellular processes, including the half transporters of the ABCB subfamily, which function in iron metabolism and transport of Fe/S protein precursors, and the members of subfamilies ABCD, ABCE and ABCF, which have roles in very long chain fatty acid transport. Both ABCE and F gene products may be involved in an innate immune response to viral infections. As in the fly, ABCH proteins are inverse half-transporters showing the same domain architecture as the members of the ABCG subfamily, and ABCG transporters involve in transportation of ommochrome precursors and uric acid into pigment granules and urate granules. Conclusion: These results paved the way for further study on the function of the ABC transporters in silkworm, Bombyx mori.