Fibrinopeptide B in fibrin assembly and metabolism: physiologic significance in delayed release of the peptide.
The delayed release of peptide B that accelerates towards the end of fibrin formation unmasks accessory (b-) epitopes for monomer interaction. Ultracentrifuge and chromatographic analysis of the composition and dissociation of soluble complexes formed by monomers in fibrinogen solution indicate that the b-epitope augments aggregation by acting cooperatively with the a-epitope to reinforce rather than cross-bridge oligomer assembly. Monomer/fibrinogen association by coordinated interactions through both epitopes is strengthened by an additional order of magnitude over associations (10(7) and 1.6 X 10(6) M-1) through the a- and b-epitopes individually, without affecting oligomer thickness. It is suggested that the delayed release of B has purpose in allowing early complexes to dissociate for (1) rapid equilibration across interstitial fluids, and for (2) rapid uptake by phagocytic cells which depend on access to the a-epitope for monomer absorption. In late stages of coagulation, stabilization of oligomer assembly imparted by the b-epitope blocks both equilibration of fibrin concentrations and phagocytic clearance of the fibrin to localize deposition.
D002850:Chromatography, Gel; D005337:Fibrin / Q000378:metabolism*; D005340:Fibrinogen / Q000378:metabolism*; D005345:Fibrinopeptide B / Q000378:metabolism*; D006801:Humans; D008958:Models, Molecular; D014461:Ultracentrifugation
D005345:Fibrinopeptide B; D005337:Fibrin; D005340:Fibrinogen