CHARACTERIZATION OF A COMPLETE IMMUNOGLOBULIN HEAVY-CHAIN VARIABLE REGION GERM-LINE GENE OF RAINBOW-TROUT

A germ-line heavy-chain variable region (V(H)) gene (RTVH431) has been isolated from a rainbow trout (Salmo gairdneri) and characterized by complete nucleotide sequencing. It is characteristic of V(H), as shown by the conserved octamer and TATA motif in the 5' region, the heptamer-nonamer recombination signal sequence in the 3' region, and the 18-amino-acid-long hydrophobic leader interrupted by an intron. The 98-amino-acid-long V(H) coding region has 50-70% nucleotide sequence homology and 40-60% amino acid sequence homology with V(H)s of various vertebrate species. We have also found unique or species-specific amino acid residues in the V(H)s of rainbow trout, amphibia (Xenopus), reptile (Caiman), and shark (Heterodontus) in our sequence analyses. The RTVH431 has an unusual amino acid in the conserved 34th position in complementarity-determining region 1 of V(H). Southern hybridization results suggest the presence of a large gene family related to RTVH431 in the trout genome. The complex evolution of antibody V genes is discussed.