Beta(Leu121-Lys122) segment of fibrinogen is in a region essential for plasminogen binding by fibrin fragment E.
It was shown previously that two sequentially nonidentical regions of human fibrin(ogen), present in fragments D and E, carry specific plasminogen-binding sites [V aradi , A., & Patthy , L. (1983) Biochemistry 22, 2440-2446]. Comparison of the affinity of a variety of fragment E species for immobilized Lys-plasminogen revealed that fragment E3e [(alpha 20/24-78, beta 54-122, gamma 1-53)2] possesses a strong plasminogen-binding site, whereas fragment E3t [(alpha 20/24-78, beta 54-120, gamma 1-53)2] has 30-fold lower affinity for the affinant . Since the two fragments differ only in the beta ( Leu121 - Lys122 ) segment, this suggests that residues beta ( Leu121 - Lys122 ), present in the triple-helical connector region of fibrin(ogen), are essential for plasminogen binding by fragment E. Reduction and alkylation of fragment E3e lead to the destruction of the plasminogen-binding site, indicating that none of the separated, alkylated polypeptide chains of the fragment are able to bind to plasminogen and probably the coiled-coil superstructure of the connector region is necessary for the maintenance of the plasminogen-binding site of fragment E.
D000595:Amino Acid Sequence; D001665:Binding Sites; D005338:Fibrin Fibrinogen Degradation Products / Q000378:metabolism*; D005340:Fibrinogen / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D010446:Peptide Fragments / Q000302:isolation & purification; D010958:Plasminogen / Q000378:metabolism*
D005338:Fibrin Fibrinogen Degradation Products; D010446:Peptide Fragments; C018543:fibrinogen fragment E; D005340:Fibrinogen; D010958:Plasminogen