title: Identification of the plasminogen-binding site of human alpha 2-plasmin inhibitor.
abstract: A plasminogen-binding site of human alpha 2-plasmin inhibitor was studied. The chromatogram of digest from the amidinated alpha 2-plasmin inhibitor (67K-daltons, plasminogen-binding form) with trypsin was almost identical with that obtained from the 65K-daltons derivative (non-plasminogen-binding form) treated with the same procedure, except for the three tryptic peptides. One of the three peptides, the deamidinated peptide T-11, was found to have a strong ability to inhibit the interaction of alpha 2-plasmin inhibitor with human plasmin. Moreover, the dissociation constant Kd for interaction between the peptide T-11 and plasmin was estimated to be 5.5 microM, indicating that Kd is about 10-fold lower than that of epsilon-aminocaproic acid. The sequence of the peptide T-11 was determined by the Edman method as follows: NH2-G-D-K-L-F-G-P-D-L-K-L-V-P-P-M-E-E-D-Y-P-Q-F-G-S-P-K-COOH. alpha 2-Plasmin inhibitor and its 65K-daltons derivative were found to have the same NH2-terminal sequence of Asn(Asp)-Gln-Glu-Gln-. These results indicated that the plasminogen-binding site(s) of alpha 2-plasmin inhibitor could be located in the COOH-terminal region of its molecule and that some of epsilon-NH2-groups in the deamidinated peptide T-11 may be involved in the lysine-binding site(s) of plasmin(ogen).
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D006868:Hydrolysis; D010446:Peptide Fragments / Q000032:analysis; D010958:Plasminogen / Q000378:metabolism*; D014357:Trypsin; D000979:alpha-2-Antiplasmin / Q000378:metabolism*
chemical_list: D010446:Peptide Fragments; D000979:alpha-2-Antiplasmin; D010958:Plasminogen; D014357:Trypsin