title: Gly-Pro-Arg-Pro modifies the glutamine residues in the alpha- and gamma-chains of fibrinogen: inhibition of transglutaminase cross-linking.
abstract: During blood clotting Factor XIIIa, a transglutaminase, catalyzes the formation of covalent bonds between the epsilon-amino group of lysine and the gamma-carboxamide group of peptide-bound glutamine residues between fibrin molecules. We report that glycyl-L-prolyl-L-arginyl-L-proline (GPRP), a tetrapeptide that binds to the fibrin polymerization sites (D-domain) in fibrin(ogen), inhibits transglutaminase cross-linking by modifying the glutamine residues in the alpha- and gamma-chains of fibrinogen. Purified platelet Factor XIIIa, and tissue transglutaminase from adult bovine aortic endothelial cells were used for the cross-linking studies. Gly-Pro (GP) and Gly-Pro-Gly-Gly (GPGG), peptides which do not bind to fibrinogen, had no effect on transglutaminase cross-linking. GPRP inhibited platelet Factor XIIIa-catalyzed cross-linking between the gamma-chains of the following fibrin(ogen) derivatives: fibrin monomers, fibrinogen and polymerized fibrin fibers. GPRP functioned as a reversible, noncompetitive inhibitor of Factor XIIIa-catalyzed incorporation of [3H]putrescine and [14C]methylamine into fibrinogen and Fragment D1. GPRP did not inhibit 125I-Factor XIIIa binding to polymerized fibrin, demonstrating that the Factor XIIIa binding sites on fibrin were not modified. GPRP also had no effect on Factor XIIIa cross-linking of [3H]putrescine to casein. This demonstrates that GPRP specifically modified the glutamine cross-linking sites in fibrinogen, and had no effect on either Factor XIIIa or the lysine residues in fibrinogen. GPRP also inhibited [14C]putrescine incorporation into the alpha- and gamma-chains of fibrinogen without inhibiting beta-chain incorporation, suggesting that the intermolecular cross-linking sites were selectively affected. Furthermore, GPRP inhibited tissue transglutaminase-catalyzed incorporation of [3H]putrescine into both fibrinogen and Fragment D1, without modifying [3H]putrescine incorporation into casein. GPRP also inhibited intermolecular alpha-alpha-chain cross-linking catalyzed by tissue transglutaminase. This demonstrates that the glutamine residues in the alpha-chains involved in intermolecular cross-linking are modified by GPRP. This is the first demonstration that a molecule binding to the fibrin polymerization sites on the D-domain of fibrinogen modifies the glutamine cross-linking sites on the alpha- and gamma-chains of fibrinogen.
authors.forename: K E
authors.initials: KE
authors.lastname: Achyuthan
authors.forename: J V
authors.initials: JV
authors.lastname: Dobson
authors.forename: C S
authors.initials: CS
authors.lastname: Greenberg
mesh_terms: D000818:Animals; D002417:Cattle; D005176:Factor XIII / Q000037:antagonists & inhibitors*; D005337:Fibrin / Q000378:metabolism*; D005340:Fibrinogen / Q000378:metabolism*; D005973:Glutamine / Q000378:metabolism*; D007700:Kinetics; D046911:Macromolecular Substances; D008744:Methylamines / Q000378:metabolism; D009842:Oligopeptides / Q000378:metabolism*; D011108:Polymers; D011700:Putrescine / Q000378:metabolism; D011503:Transglutaminases / Q000037:antagonists & inhibitors
chemical_list: D046911:Macromolecular Substances; D008744:Methylamines; D009842:Oligopeptides; D011108:Polymers; D005973:Glutamine; C034585:glycyl-prolyl-arginyl-proline; D005337:Fibrin; D005340:Fibrinogen; D005176:Factor XIII; D011503:Transglutaminases; D011700:Putrescine