A neoantigenic determinant in the D-dimer fragment of fibrin.

Monoclonal antibody (mAb) III-3b binds D-dimer with K(d)=1.4 x 10(-10) M without cross-reaction with fibrin(ogen). The epitope for this mAb is in Bbeta134-190, presumably in Bbeta155-160. The latter site is buried in the coiled coil structure of fibrin(ogen) but it is exposed as a neoantigenic determinant in D-dimer upon plasmic lysis of fibrin. mAb III-3b may be used as a tool for immunodiagnostic quantification of D-dimer in blood plasma.

Polymerization sites in the D-domain of human fibrin(ogen).

The present work deals with localization of previously unknown polymerization sites of the fibrin DD-fragment. D-dimer we obtained has a pronounced inhibitory effect on fibrin polymerization (IC50 = 0.06 microM). The inhibitory effect of the DD-fragment disappeared after reduction and carboxymethylation. However, polypeptide chains betaDD (Bbeta134-461) and gammagammaDD (gamma63-411)2 of the DD-fragment, isolated by preparative electrophoresis, displayed their inhibitory activity. For instance, the rates of fibrin protofibril lateral association were decreased twice in the presence of betaDD and gammagammaDD chains at their molar ratios to fibrin of 0.40 and 0.15, respectively. The IC50 values for betaDD and gammagammaDD were 0.24 and 0.10 microM, respectively. Highly specific inhibition of protofibril lateral association suggests that the protofibril lateral association sites are located in Bbeta134-461 and gamma63-411 regions of the fibrin D-domain. Our data confirm those reported by Doolittle et al. regarding the gamma-chain and a hypothesis about beta-chain of fibrin D-domain (Yang, Z., Mochalkin, I., and Doolittle, R. F. (2000) Biochemistry, 97, 14156-14161).

[Effect of chemical modification of arginine residues of fibrinogen and its DH-fragment on the rate of hydrolysis of these proteins by plasminogen]. / Vliianie khimicheskoi modifikatsii ostatkov arginina fibrinogena i ego DH-fragmenta na skorost' gidroliza étikh belkov plazminom.

Plasminolysis of the fibrinogen arginine and its DH-fragment residues was sufficiently lower in contrast to that of initial proteins. It is supposed that the decrease of the speed of the process is the result of the blocking of centres, adequate to arginyl-binding sites of plasmin molecule.

[Features of the interaction of Glu- and Lys-forms of plasminogen with native and partially hydrolyzed fibrin]. / Osobennosti vzaimodeistviia Glu- i Lys-form plazminogena s nativnym i chastichno gidrolizovannym fibrinom.

Glu- and Lys-plasminogen interaction with native and desAABB-fibrin obtained from fibrinogen partially hydrolyzed by plasmin was studied. It was found that native fibrin adsorbs 6 times more Lys-plasminogen as compared to the native form of the proenzyme. The range of the Lys-plasminogen binding does not change, if part of the fibrinogen molecules hydrolyze down to X-fragments. At the same time, the appearance in the system of 1% Xi-fragments leads to a 6-fold increase in the Glu-plasminogen binding. The amount of adsorbed Glu-plasminogen reaches the level of Lys-plasminogen adsorption both in the native and partially hydrolyzed fibrin. It was found that kringle K 1-3 or 6-aminohexanoic acid at saturating for high-affinity lysine-binding sites concentrations do not influence the Glu-plasminogen binding to native fibrin but inhibit it when the partially purified form is used. It is assumed that the manyfold increase of the Glu-plasminogen binding to partially hydrolyzed fibrin is due to the alteration of the proenzyme conformation at the initial steps of fibrin hydrolysis during the formation of Xi fragments.

[The effect of arginine on hydrolysis of fibrinogen by plasmin and mini-plasmin]. / Vliianie arginina na gidroliz fibrinogena plazminom i mini-plazminom.

The rate of plasmin or Val442-plasmin catalyzed hydrolysis of fibrinogen decreases several times as affected by arginine in high concentrations. The enzyme is shown to be not inhibited by arginine. The observed effect is supposed to depend on saturation of the protein-proteins interaction sites located between 442 and 790 amino acid residues.

[Proteolytic activity of the Glu-plasminogen complex with fibrinogen fragment E]. / Issledovanie proteolitcheskoi aktivnosti kompleksa Glu-plasminogena s fragmentom E fibrinogena.

Glu-plasminogen interaction with fibrinogen fragment E results in the alteration of its adsorptive capacity. During this interaction in the absence of plasmin and tissue activator of plasminogen, Glu-plasminogen is transformed into a partly degraded form. Glu-plasminogen complexes with soluble and immobilized fibrinogen fragment E. contain a serine proteinase-specific activity which is inhibited by diisopropylfluorophosphate. The complexes under study are active towards fibrin and the plasmin-specific tripeptide substrate, D-Val-L-Leu-L-Lys-p-nitroanilide. It is concluded that fibrinogen fragment E induces structural changes in the enzyme molecule which eventually result in the formation of an active center.