[The role of D2-E2 centers of interdomain binding of fibrin monomer during fibrinogen co-polymerization with an NH2-terminal disulfide knot of fibrin].

Copolymerization of fibrinogen with desAB- and desA-fibrin NH2-terminal disulfide knots (tN-DSK and rN-DSK, respectively) caused by interdomain D-E-binding was compared. It was shown that only tN-DSK effectively produces with fibrinogen soluble and insoluble forms of the copolymer characterized by a constant stoichiometry which, in turn, reflects its regular structure. Fibrinogen and rN-DSK complexing is weakly expressed. No soluble complexes were identified. A small quantity of insoluble complexes formed had no constant stoichiometry which points to the variability of their structure. It is concluded that the formation of the regular polymer structure during fibrinogen and fibrin N-DSK complex formation requires the participation of two types of complementary centers, namely: D1-E1 and D2-E2. This conclusion was confirmed by disturbances in fibrinogen and tN-DSK copolymerization at pH 6.5, when the function of the E2-center was inhibited. The significance of these findings for the understanding of the mechanisms of two types of D-E center function during fibrin clotting is discussed.