Amino Acid Sequence Ala-Asp-Ser-Gly-Glu-Gly-Asp-Phe-Leu-Ala-Glu-Gly-Gly-Gly-Val-Arg Biochem/physiol Actions Fibrin polymerization is initiated by thrombin cleavage of fibrinopeptide A from fibrinogen α chains, exposing two E domain E(A) sites. The phenylalanine at α chain residue 8 is important for efficient thrombin-catalyzed proteolysis of fibrinogen. Substitution of tyrosine for phenylalanine blocks sequential fibrinopeptide release and, thus, blocks polymerization and clot formation. |