Basic characterization of avian NK-lysin (NKL) from the Japanese quail, Coturnix japonica

We identified an antimicrobial cationic peptide that was expressed in the natural killer cells and cytotoxic T-lymphocytes of Japanese quail. The gene, designated CjNKL, was located downstream of AEBP1L and POLD2 in a region syntenic with the chicken genome. CjNKL comprised four exons, as does chicken GgNKL. The coding sequence in CjNKL was 411 bp long and exon 3 of CjNKL lacked 9 bp when compared to chicken GgNKL, but CjNKL and GgNKL were 81% identical at the nucleic acid level. The saposin like type-B domain of CjNKL contained the six essential cysteines, one proline, 15 cationic amino acids residues, and an antibacterial region that are characteristic of NKL proteins. The 5' flanking region of CjNKL contained positive regulatory elements, an activator protein-1 binding site and two nuclear factor (NF)-B binding sites, and a negative regulatory element, CAAT/enhancer binding protein (C/EBP) binding site. However, the number of NF-B sites and C/EBP sites within CjNKL are fewer than the number within GgNKL. Additionally, we confirmed that CjNKL was transcribed in at least 18 tissues, including immune and digestive tissues. These data indicated that transcriptional activation of CjNKL differed slightly from those of GgNKL.