[Mechanism of the formation of complexes between monomer fibrin and the inhibitor of its polymerization - fragment D].
It was found that fragment D derived from fibrinogen may be coupled with the fibrin monomer to produce complexes of unstable and stable types. The native fibrin monomer forms unstable complexes; the stable ones arise when the labile peripheral domains of the fibrin molecules are reversibly modified and their specific intermolecular affinity for the thrombin-activated central domains is lowered or eliminated. Fragment D, the free peripheral domain possessing polymerization centers, is strongly bound to the modified monomer occupying the polymerization sites of its central domain. The modification was induced by using acid pH (around 3.7) or by urea or NaBr taken at concentrations which caused no denaturation. In neutral media the acid-modified monomer passes to its normal state which is accompanied by simultaneous decrease of fragment D binding and restoration of codgulability. Fragment D presumably competes with the peripheral domain for the central one. Peripheral domains of the intact monomer are predominant competitors; fragment D only reduces the rate of polymerization due to temporary complex formation. However, modification results in a formation of stable complexes and thus decreases the accumulation of polymeric fibrin.
D000818:Animals; D002417:Cattle; D005337:Fibrin / Q000378:metabolism*; D005338:Fibrin Fibrinogen Degradation Products / Q000502:physiology*; D007700:Kinetics; D046911:Macromolecular Substances
D005338:Fibrin Fibrinogen Degradation Products; D046911:Macromolecular Substances; C015214:fibrinogen D fragment; D005337:Fibrin
Mekhanizm obrazovaniia kompleksov mezhdu monomernym fibrinom i ingibitorom ego polimerizatsii--fragmentom D.