Interaction of the fibronectin COOH-terminal Fib-2 regions with fibrin: Further characterization and localization of the Fib-2-binding sites

Incorporation of fibronectin into fibrin clots is important for the formation of a provisional matrix that promotes cell adhesion and migration during wound healing. Previous studies revealed that this incorporation occurs through noncovalent interaction between two NH2-terminal Fib-1 regions of fibronectin (one on each chain) and the αC-regions of fibrin, and is further reinforced by factor XIIIa-mediated covalent cross-linking of fibronectin to the fibrin matrix. To clarify the role of another pair of fibrin-binding regions, Fib-2, located at the disulfide-linked COOH-terminal ends of fibronectin, we prepared by limited proteolysis a dimeric 140 kDa (Fib-2)2 fragment containing both Fib-2 regions and tested its interaction with recombinant fragments corresponding to the αC regions of fibrin(ogen). In both ELISA and surface plasmon resonance (SPR) experiments 140 kDa (Fib-2)2 bound to the immobilized Aα221−610 αC-fragment. However, the affinity of binding was substantially lower than that for Fib-1. Liga...