1997 年 121 巻 2 号 p. 278-287
Two groups of anti-plasminogen monoclonal antibodies, whose epitope was either in the kringle 1+2+3 domain (F3P2, F11P5, F11P6, and F12P18) or the kringle 5 domain (F1P6 and F12P16), were isolated and their effects on the conformation of plasminogen were explored. All antibodies except F1P6 had 3- to 10-fold higher affinity toward Lys-plasmino-gen than Glu-plasminogen. F1P6 exhibited a comparable affinity to Glu- and Lys-plasmino-gen. Among these, only F11P5 binding was inhibited by ε-amino-n-caproic acid (EACA) in a concentration-dependent manner, with half maximal inhibition at 3 mM. From a competi-tion assay, we concluded that the epitopes of F11P5, F11P6, and F12P18 should be very close, and located at or near the low affinity lysine binding site on the kringle 2+3. These three antibodies dramatically enhanced the binding of Glu-plasminogen to the other antibodies, except to F1P6. Interestingly, F3P2, whose non-overlapping epitope was in the kringle 2+3 domain, also augmented the binding of Glu-plasminogen to the other anti-bodies. In contrast, we did not observe enhanced binding of Lys-plasminogen to one antibody in the presence of the other antibodies, and the binding of Glu-plasminogen to these antibodies did not increase in the presence of 10 mM EACA. In the presence of these antibodies, including F1P6, Glu-plasminogen bound more efficiently to immobilized degraded fibrin, with a binding profile similar to Lys-plasminogen. All antibodies except F1P6 enhanced the conversion rate of plasminogen to plasmin remarkably. Taken together, we propose that these two groups of monoclonal antibodies can dissociate the intramole-cular interactions of Glu-plasminogen and induce the conformational transition of Glu-plasminogen to Lys-plasminogen. In addition, the kringle 2 +3 and kringle 5 structures of Glu-plasminogen liganded with EACA are distinct from the Lys-plasminogen structure.
