Genomic structure of keratinocyte transglutaminase. Recruitment of new exon for modified function.
The gene for keratinocyte transglutaminase (TGK) spans 14 kilobase pairs and contains 15 exons. Many features of the TGK gene are very similar, if not identical, to those of the gene encoding the catalytic subunit of human clotting factor XIII: they have the same number of exons, corresponding introns always interrupt the coding region in the same phase of the codon, and most exons are of similar size (10 or 15 are exactly the same size). In these respects, the TGK and factor XIII catalytic subunit genes resemble each other more than either resembles the gene for erythrocyte band 4.2, a noncatalytic transglutaminase superfamily member. Exon II in both the TGK and factor XIII genes encodes an amino-terminal extension of nonhomologous sequence which in each protein confers a specialized function (membrane anchorage or activation of cross-linking, respectively). This suggests that the evolution of these genes included recruitment of a new exon to modify the enzyme action. Southern blots of genomic DNA reveal the presence of a TGK-like gene in birds, amphibians, and fish, but not in flies.
Department of Environmental Toxicology, University of California, Davis 95616-8588.
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Phillips
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Stewart
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D000595:Amino Acid Sequence; D001483:Base Sequence; D005075:Biological Evolution; D001798:Blood Proteins / Q000235:genetics; D015139:Blotting, Southern; D003598:Cytoskeletal Proteins; D004247:DNA / Q000235:genetics; D004910:Erythrocyte Membrane / Q000378:metabolism; D005091:Exons; D005176:Factor XIII / Q000235:genetics; D006801:Humans; D007438:Introns; D015603:Keratinocytes / Q000201:enzymology*; D008565:Membrane Proteins; D008969:Molecular Sequence Data; D005810:Multigene Family; D009693:Nucleic Acid Hybridization; D016133:Polymerase Chain Reaction; D012326:RNA Splicing; D015183:Restriction Mapping; D016415:Sequence Alignment; D011503:Transglutaminases / Q000235:genetics*
D001798:Blood Proteins; D003598:Cytoskeletal Proteins; D008565:Membrane Proteins; C044791:erythrocyte membrane band 4.2 protein; D004247:DNA; D005176:Factor XIII; D011503:Transglutaminases