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.