Fibrinogen αC Domains Contain Cryptic Plasminogen and tPA Binding Sites

: Surface plasmon resonance and ELISA experiments revealed that recombinant fibrinogen αC fragment (residues Aα221–610) corresponding to the αC domain binds tPA and plasminogen with high affinity. This binding was found to be Lys-dependent and occurred via independent binding sites. Study with truncated variants of the αC fragment located these sites in its COOH-terminal half. Binding of tPA and plasminogen to these sites stimulated activation of the latter whereas proteolytic degradation of the αC fragment reduced this effect substantially, suggesting the importance of the αC domains in regulation of fibrinolysis.