Molecular cloning and evolution of transferrin cDNAs in salmonids

Transferrin complementary DNAs were cloned from the livers of seven species in three genera of salmonids (kokanee salmon Oncorhynchus nerka, amago sal mon Oncorhynchus masou ishikawa, masu salmon Oncorhynchus masou masou, Japa nese char Salvelinus pluvius, brook trout Salvelinus fontinalis, lake trout Salvelinus namaycush, and brown trout Salmo trutta) subsequent to polymera se chain reaction amplification with primers derived from conserved regions of transferrin cDNA sequences. The transferrin cDNAs of the seven species of salmonids had sizes of 2.2 to 2.4 kb and encoded an open reading frame c onsisting of 691 amino acids with a putative signal peptide of 18 amino aci ds. The alignment of salmonid transferrin cDNAs showed a duplicated structu re and conserved anion-binding residues, iron-binding residues, and cystein e residues for disulfide bridges. The deduced amino acid sequences of the s even salmonid transferrin cDNAs share 85% to 99% homology. A phylogenetic t ree of amino acid sequences of transferrin cDNAs from salmonids showed that the relationship among the three genera of salmonids (Oncorhynchus, Salvel inus, and Salmo) is well correlated with that derived from classic morpholo gic and genetic analyses.