Specificity of Fibronectin‐fibrin Cross‐linking*

Our experiments indicate that (1) non-covalent binding of fibronectin to fibrin is mediated by sites in a 27 kd NH2-terminal region and a 31 kd COOH-terminal region of fibronectin; (2) the 31 kd region is probably present in both chains of the fibronectin dimer; and (3) covalent (factor XIIIa-mediated) cross-linking of fibronectin and fibrin is between a glutaminyl residue in the 27 kd region of fibronectin and a lysyl residue in the COOH-terminal two-thirds of the fibrin alpha chain.