Exon/intron structure of the human transferrin receptor gene.

A PCR-based intron jumping strategy has been utilized to investigate the exon/intron structure of the human transferrin receptor gene and determine the sequences of exon/intron junctions. There are 18 exons and introns 5' to a large exon encoding the last translated segment and a sizable 3' untranslated segment. All of the translated segments are encoded by exons 2-19. The tight turn motif, which is critical to the process of endocytosis, is encoded by exon 3. Based on recent studies of human/chicken receptor chimeras, it appears that the residues most likely to be involved in transferrin binding are encoded by exons 17-19. Exon 12 exhibits the greatest degree of homology with the gene for the prostate specific membrane antigen. A polymorphism has been tentatively identified at nucleotide position 519 in exon 4; the presence of either adenine or guanine should result in either serine or glycine, respectively, at position 142 of the amino acid sequence. This analysis of genomic structure will permit further detailed studies of the regulation, expression and evolution of the human transferrin receptor gene.