Abstract
Lymphocyte cell kinase ( LCK ) belongs to the Src family of tyrosine kinases, which involves in the proliferation control of lymphocytes. In this study, we cloned the LCK gene of humphead snapper ( Lutjanus sanguineus ) (designed as Ls LCK ). Sequence analysis showed that the full‐length cDNA of Ls LCK was 2279 bp, contained a 1506‐bp open reading frame ( ORF ), encoding a polypeptide of 501 amino acids. The deduced amino acid possessed the typical structural features of known LCK proteins, including four Src homology ( SH ) domains arranged as the SH 1 domain followed by a regulatory C‐terminal tail ( COOH ‐domain), SH 2 and SH 3 adapter domains and SH 4 domain which required for membrane attachment and CD 4/ CD 8 binding. Fluorescent quantitative real‐time PCR analysis indicated that Ls LCK transcripts were expressed mainly in thymus, spleen and head kidney in healthy fish. Moreover, the mRNA expressions in these tissues were significantly up‐regulated after challenge with Vibrio harveyi . The results of immunohistochemistry showed that Ls LCK protein localized distinctly in cytoplasm of cell in thymus, spleen and head kidney. Taken together, these findings indicated that Ls LCK may play an important role in the immune response of humphead snapper against bacterial infection.