Studies on tissue transglutaminases : interaction of erythrocyte type-2 transglutaminase with GTP

• Published in: Biochemical journal Vol. 291; no. 1; pp. 37 - 39
• Main Authors: BERGAMINI, C. M, SIGNORINI, M
• Format: Journal Article
• Language: English
• Published: Colchester Portland Press 01.04.1993
• Subjects: Affinity Labels; Analytical, structural and metabolic biochemistry; Binding Sites; Biological and medical sciences; Borohydrides - pharmacology; Calcium - pharmacology; Enzymes and enzyme inhibitors; Erythrocytes - enzymology; Fundamental and applied biological sciences. Psychology; Guanosine Triphosphate - analogs & derivatives; Guanosine Triphosphate - metabolism; Guanosine Triphosphate - pharmacology; Humans; Oxidation-Reduction; Periodic Acid; Transferases; Transglutaminases - metabolism; Stoichiometry; GTP; Enzymatic activity; Calcium; Enzyme; Red blood cell; Binding site; Protein-glutamine γ-glutamyltransferase; Structure function relationship
• ISSN: 0264-6021; 1470-8728
• DOI: 10.1042/bj2910037

Ca2+ and GTP are the main modulators of type-2 transglutaminases. To study the interaction of the enzyme with GTP, we have employed periodate-oxidized GTP as an affinity-label probe. Dialdehyde GTP bound irreversibly to type-2 transglutaminase in a time-dependent way with 1:1 stoichiometry at complete modification. The reaction took place in the absence, but was more rapid in the presence, of cyanoborohydride. Native GTP prevented incorporation of dialdehyde GTP, and Ca2+ significantly slowed down the reaction rate. The modified enzyme displayed decreased sensitivity to Ca2+, with a sigmoid saturation curve. We conclude that type-2 transglutaminase has a single GTP-binding site, the modification of which by dialdehyde GTP mimics nucleotide binding to the enzyme.