Molecular Characteristic and Responsive Expression of Arginine Kinase in the Mud Crab, Scylla paramamosain

Arginine kinase (AK) is a phosphor-transferase which plays a critical role in energy metabolism in invertebrates. Using reverse transcription-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE) PCR, this study successfully cloned a 1469 bp full-length complementary DNA (cDNA) of AK from the mud crab, Scylla paramamosain (designated as SpAK). The open-reading frame (ORF) of SpAK was 1071 bp, encoding 357 amino acids. The predicted protein showed a high level of identity to known AK from other invertebrates and creatine kinase (CK) from vertebrates that belongs to a conserved family of ATP: guanidine phosphotransferases. The SpAK gene contains two exons and one intron. The quantitative real-time PCR analysis revealed a broad expression of SpAK in various tissues. After challenge with the bacterium Vibrio alginolyticus, the peak value of AK expression in hepatopancreas increased 17-fold (at 3 h), and 15-fold (at 72 h) in hemolymph, as compared to the control. The present research suggests that AK might be involved in immune response of the mud crab, S. paramamosain.