Abstract
In this study, the complementary (c)DNA sequence encoding orange‐spotted grouper Epinephelus coioides Tak1 ( ectak1 ) was cloned, which has an open reading frame of 1728 bp that encodes 575 amino acids (aa). Sequence analysis indicated that Ectak1 contains two characteristic conserved domains, i.e . an N‐terminal serine–threonine protein kinase catalytic domain (27–275 aa) and a C‐terminal coiled‐coil region (499–562 aa). Ectak1 shares high sequence identity with Tak1 from other fish species, especially those of Nile tilapia Oreochromis niloticus (96%) and zebra mbuna Maylandia zebra (96%). ectak1 transcripts were expressed broadly in all of the tissues tested, but ectak1 expression was reduced mainly in the local infection sites (skin and gill) after infection with Cryptocaryon irritans . Intracellular localization analysis showed that Ectak1 was distributed mainly in the cytoplasm. A luciferase reporter assay showed that Ectak1 significantly impaired the NF ‐κ B activity induced by E. coioides Myd88 and Traf6. Overall, these results suggest that Ectak1 functions to reduce the activity of NF ‐κ B induced by toll‐like receptor ( TLR ) signal molecules in HEK‐293T cells, and it might have an important role in host defences against parasitic infections.