title: Studies on tissue transglutaminases: interaction of erythrocyte type-2 transglutaminase with GTP.
abstract: 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.
authors.affiliation: Instituto di Chimica Biologica, Università di Ferrara, Italy.
authors.forename: C M
authors.initials: CM
authors.lastname: Bergamini
authors.forename: M
authors.initials: M
authors.lastname: Signorini
mesh_terms: D000345:Affinity Labels; D001665:Binding Sites; D001894:Borohydrides / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D004912:Erythrocytes / Q000201:enzymology*; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D006801:Humans; D010084:Oxidation-Reduction; D010504:Periodic Acid; D011503:Transglutaminases / Q000378:metabolism*
chemical_list: D000345:Affinity Labels; D001894:Borohydrides; D010504:Periodic Acid; C037756:2-(guanylformylmethoxy)-3-(triphospho)propanal; D006160:Guanosine Triphosphate; C009282:sodium cyanoborohydride; D011503:Transglutaminases; D002118:Calcium