Cross-linking of fibronectin to C-terminal fragments of the fibrinogen alpha-chain by factor XIIIa.

Fibronectin binds specifically to fibrin and is covalently cross-linked to the fibrin alpha chain by activated factor XIII (XIIIa). This reaction is important for wound healing. Here we investigate XIIIa-catalyzed cross-linking of fibronectin and some of its fragments to a recombinant fragment representing the COOH-terminal 30 kDa of the fibrin alpha chain (alpha C30K:His 368-Val 610). Only fibronectin and those fragments containing an intact NH2-terminus were able to form cross-linked complexes. As many as 10 of the 17 lysines in alpha C30K can serve as amine donors in this reaction. Analysis of the rate of XIIIa-catalyzed cross-linking of fibronectin NH2-terminal peptides and fragments with alpha C30K revealed that the presence of the first type I "finger" module accelerates the cross-linking reaction; addition of fingers 2-5 had no further effect.