POLYMORPHISM IN THE CODING SEQUENCE OF THE HORSE TRANSFERRIN GENE

Transferrin, the iron transport protein of the blood, is highly polymo rphic in many species, including the horse. A number of sequence polym orphisms that distinguish several of the variants of horse transferrin are reported here. Previous studies indicated that exons 12 and 15 we re likely to be polymorphic. Sequencing regions of exons 12 and 15 fro m D and R variants revealed 10 nucleotide substitutions that encoded s ix amino acid replacements. The F-1, F-2, H-2, and variants were ide ntical to D, and the O variant was almost identical to R, in the regio ns studied. The data indicated that the horse transferrin variants mak e up two distinct groups. The positions of differences between the D a nd F-1 alleles were determined by analyzing single-stranded conformati on polymorphisms. Sequencing then revealed three nucleotide substituti ons, two of which encoded amino acid substitutions. Location of the ei ght polymorphic residues on the three-dimensional structure of human l actoferrin revealed that all were clustered at one end of the C-lobe.