CDNA cloning, characterization and expression analysis of ATP-binding cassette transmembrane transporter in Exopalaemon carinicauda

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ATP-binding cassette (ABC) transporters are integral membrane proteins which carry diverse substrates across biological membranes. In this study, we report the cloning of a full-length, 2468-bp cDNA sequence encoding a gene of the ABC transporter subfamily G (ABCG) from the shrimp Exopalaemon carinicauda (E. carinicauda). The deduced protein, EcABCG, contains 627 amino acid residues, with a theoretical molecular weight of 69.0 kDa. Phylogenetic analysis showed that EcABCG shares the highest identity with the homologs of the shrimp species Litopenaeus vannamei and Fenneropenaeus chinensis, and is also closely related to the insect ABC transporter/white proteins. High-level mRNA expression of EcABCG was detected in the tissue of the hepatopancreas and intestine, using a real-time quantitative reverse-transcriptase PCR. The ABC transporter mRNA transcript in the hepatopancreas of E. carinicauda was significantly upregulated after 6 h and after 1 h of exposure to acidic and alkaline conditions respectively. EcABCG was also induced in the intestine at 1–24 and 3–48 h after exposure to acidic and alkaline conditions respectively. Upon exposure to sulfamerazine diets (50, 100 and 200 mg kg−1) for 3 and 6 h, respectively, the mRNA expression of EcABCG was upregulated in the hepatopancreas. EcABCG was also induced in the intestine after exposure to 50, 100 and 200 mg kg−1 sulfamerazine diets for 6, 3 and 12 h respectively. These results suggest that the ABCG transporter of E. carinicauda might play a role in coping with pH stress and in exporting xenobiotics.