Gallinacin-3, an inducible epithelial beta-defensin in the chicken

Gallinacin-3 and gallopavin-1 (GPV-1) are newly characterized, epithelial P -defensins of the chicken (Gallus gallu) and turkey (Meleagris gallopavo), respectively. In normal chickens, the expression of gallinacin- was especia lly prominent in the tongue, bursa of Fabricius, and trachea. It also occur red in other organs, including the skin, esophagus, air sacs, large intesti ne, and kidney. Tracheal expression of gallinacin- increased significantly after experimental infection of chickens with Haemophilus paragallinarum, w hereas its expression in the tongue, esophagus, and bursa of Fabricius was unaffected. The precursor of gallinacin-3 contained a long C-terminal exten sion not present in the prepropeptide. By comparing the cDNA sequences of g allinacin-3 and GPV-1, we concluded that a 2-nucleotide insertion into the gallinacin-3 gene had induced a frameshift that read through the original s top codon and allowed the chicken propeptide to lengthen. The striking stru ctural resemblance of the precursors of beta -defensins to those of crotami nes (highly toxic peptides found in rattlesnake venom) supports their homol ogy, even though defensins are specialized to kill microorganisms and crota mines are specialized to kill much larger prey.