Related Experiment Video
Updated: Oct 5, 2026

Evaluation of Protein–Protein Interactions using an On-Membrane Digestion Technique
Published on: July 19, 2019
Transglutaminase 5 cross-links loricrin, involucrin, and small proline-rich proteins in vitro
1Biochemistry Laboratory, Istituto Dermopatico dell' Immacolata-Istituto di Ricerca e Cura a Carattere Scientifico, Department of Experimental Medicine and Biochemical Sciences, University of Rome Tor Vergata, Rome, Italy.
Abstract:
Transglutaminases (TGases) are seven enzymes, cross-linking proteins by gamma-glutamil-epsilon-lysine bonds, four of which are expressed in the skin. A new member of the TGase family, TGase 5, has been identified recently, and in the present study we evaluated its role in keratinocyte differentiation in vitro. In addition to the previously described isoforms, full-length TGase 5 and Delta3 (deletion of exon 3), we identified two new splicing variants, Delta11 and Delta3Delta11 (deletion of exons 11 or 3, 11). We expressed full-length TGase 5, Delta3, Delta11, and Delta3Delta11 isoforms in the keratinocyte and baculovirus systems. The results indicate that both full-length TGase 5 and Delta11 are active, whereas Delta3 and Delta3Delta11 have very low activity. Expression studies show that full-length TGase 5 is induced during the early stages of keratinocyte differentiation and is differently regulated in comparison with the other epidermal TGases. Kinetic and in vitro cross-linking experiments indicate that full-length TGase 5 is very efficient in using specific epidermal substrates (loricrin, involucrin, and SPR3). In keratinocyte expression system, TGase 5 isoforms are retained in an intermediate filament-enriched fraction, suggesting its association with insoluble proteins. Indeed, TGase 5 co-localize with vimentin and it is able to cross-link vimentin in vitro.
Related Concept Videos
Laminins are the Adhesive Proteins of Basal Lamina
In humans, the five forms of alpha chains are LAMA 1, LAMA 2, LAMA 3, LAMA 4, and LAMA 5. The four forms of beta chains are LAMB 1, LAMB 2, LAMB 3, and LAMB 4. The three forms of gamma...
Cytoskeletal Linker Proteins - Plakins
Protein Folding Quality Check in the RER
Structural Protein Function
Collagen, the most abundant protein in mammals, is found throughout the body. In connective tissue, such as skin, ligaments, and tendons, it provides tensile strength and elasticity. In bones and teeth, it mineralizes to form...
Proteoglycans
Intracellular Signaling Affects Focal Adhesions
Some...
