Phillips M A, Stewart B E, Rice R H
Department of Environmental Toxicology, University of California, Davis 95616-8588.
J Biol Chem. 1992 Feb 5;267(4):2282-6.
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.
角质形成细胞转谷氨酰胺酶（TGK）基因跨度为14千碱基对，包含15个外显子。TGK基因的许多特征即便不完全相同，也与编码人凝血因子XIII催化亚基的基因非常相似：它们的外显子数量相同，相应的内含子总是在密码子的同一相位打断编码区，并且大多数外显子大小相似（10个或15个外显子大小完全相同）。在这些方面，TGK基因和因子XIII催化亚基基因彼此间的相似程度超过它们与红细胞带4.2基因（一种非催化性转谷氨酰胺酶超家族成员）的相似程度。TGK基因和因子XIII基因的外显子II均编码一段非同源序列的氨基末端延伸，该延伸在每种蛋白质中分别赋予一种特殊功能（分别为膜锚定或交联激活）。这表明这些基因的进化过程包括招募一个新的外显子来改变酶的作用。基因组DNA的Southern印迹显示鸟类、两栖动物和鱼类中存在一个类似TGK的基因，但在果蝇中不存在。
