A toxin-like gene in rainbow trout: cloning, expression, and gene organization.

The 'three-finger' protein family consists of structurally related proteins which display a variety of biological functions. Snake venom alpha-neurotoxins, Ly-6 alloantigens, urokinase-type plasminogen activator receptor (uPAR) and the complement regulatory protein CD59 are members of this protein family. Their characteristic feature is the disposition of four disulfide bridges forming a hydrophobic core. Here it is reported the cloning and characterization of a toxin-like gene (toxin-1) in the rainbow trout (Oncorhynchus mykiss). Phylogenetic analysis showed that trout toxin-1 classified into the short-chain neurotoxins (60-65 residues), confining to a distinct group. Trout toxin-1 gene contains three exons interrupted by two introns, in line with the other toxin members of the 'three-finger' family. Trout liver, brain, and spleen express the toxin-1 gene and its encoded protein is identified in trout plasma. This is the first report of a toxin-like gene which has been described so far in teleost.