Primary structure of keratinocyte transglutaminase.

Abstract

The nucleotide and deduced amino acid sequences of the coding regions of human and rat keratinocyte transglutaminases (protein-glutamine: amine y-glutamyltransferase; EC 2.3.2.13) have been determined. These yield proteins of -90 kDa that are 92% identical, indicative of the conservation of important structural features. Alignments of amino acid sequences show substantial similarity among the keratinocyte transglutaminase, human clotting factor XIII catalytic subunit, guinea pig liver tissue transglutaminase, and the human erythrocyte band-4.2 protein. The keratinocyte enzyme is most similar to factor XIII, whereas the band-4.2 protein is most similar to the tissue transglutaminase. A salient feature of the keratinocyte transglutaminase is its 105-residue extension beyond the N terminus of the tissue transglutaminase. This extension and the unrelated activation peptide of factor XIII (a 37-residue extension) appear to be added for specialized functions after divergence of the tissue transglutaminase from their common lineage.During terminal differentiation, keratinocytes of the epidermis and other stratified squamous epithelia synthesize an envelope consisting of cross-linked protein beneath the plasma membrane (1). Localization of the envelope appears due to the presence of a membrane-bound transglutaminase (2, 3) and several of its substrate proteins at the cell periphery (4). The enzyme is anchored in the membrane by acylated fatty acid (5) and is activated by flux of Ca2+ into the cytoplasm when cellular membranes lose their integrity during the final maturation stage (6). The biochemical events resulting in mature envelopes have been difficult to follow due to the intractable nature of the highly cross-linked product. In view of the many proteins and amines in keratinocytes serving as transglutaminase substrates (4, 7), further study of the enzyme structure may help in analysis of this process. In addition to acylation, for example, phosphorylation of the membrane anchorage region has been seen, which could alter the interaction of the enzyme with potential substrate proteins (8).The blood clotting factor XIII catalytic subunit (9-11) and tissue transglutaminase (12) have recently been cloned and sequenced. These enzymes are distantly related to each other but display significant similarity in certain regions, especially around the active site. An origin of the latter region in common with thiol proteases has been proposed (9). The more recent demonstration of striking similarity between the active site and a corresponding region in the erythrocyte band-4.2 protein (13, 14), however, indicates that closer relatives of transglutaminases exist. A cDNA clone for the keratinocyte-specific enzyme of the rabbit was originally identified by using an oligonucleotide probe directed toward the active site and was partially sequenced (15). Using that clone as probe, we have now cloned and determined the complete primary structure of this third type of transglutaminase for the human and rat.O Although many type...

Differential alternative splicing of human transglutaminase 4 in benign prostate hyperplasia and prostate cancer

“…However, transglutaminase 4-M2 would use the third initiation codon to produce functional protein product, instead of the first ATG, as described before. It is of interest that the first 10 nucleotides of human transglutaminase 4 (ATG-ATGGATG) are identical to those of human transglutaminase 1 (Kim et al, 1992, Phillips et al, 1990. Although human transglutaminase 1 also has two variants generated by utilizing different initiation codons, the amino acid sequence difference between two variants is resulted from allelic variation in the human population, instead of an alternative splicing mechanism (Kim et al, 1992).…”

Consequences of Seven Novel Mutations on the Expression and Structure of Keratinocyte Transglutaminase

“…Nucleotides have been numbered according to Phillips et al (26). To number amino acids, the first methionine of the open reading frame (15) was designated as number 1. For inheritance analysis in families, DNA was amplified by PCR, digested with restriction enzymes, and separated on agarose or polyacrylamide gels.…”

Expression of tissue transglutaminase in the developing chicken limb is associated both with apoptosis and endochondral ossification

“…9,10 In addition to these extracellular transglutaminases, there are several intracellular transglutaminases that are also involved in very specialized cross-linking reactions. Keratinocyte transglutaminase 11,12 is an intracellular enzyme that is induced during the terminal differentiation of squamous epithelial cells. Activation of this enzyme and the subsequent cross-linking of keratinocyte-specific substrate proteins lead to the formation of the cornified envelope that invests the interior of the differentiated cell.…”