The Solution Phase Interaction between Apolipoprotein(a) and Plasminogen Inhibits the Binding of Plasminogen to a Plasmin-Modified Fibrinogen Surface
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- 作者：Waheed Sangrar ; Brent R. Gabel ; Michael B. Boffa ; John B. Walker ; Mark A. Hancock ; Santica M. Marcovina ; Anton J. G. Horrevoets ; Michael E. Nesheim ; and Marlys L. Koschinsky
- 刊名：Biochemistry
- 出版年：1997
- 出版时间：August 26, 1997
- 年：1997
- 卷：36
- 期：34
- 页码：10353 - 10363
- 全文大小：226K
- 年卷期：v.36,no.34(August 26, 1997)
- ISSN：1520-4995
文摘
In the present study, we assessed the binding ofrecombinant forms of apolipoprotein(a) [r-apo(a)] to plasminogen. Apo(a)-plasminogen interactions weredemonstrated to be lysine-dependent, asthey were abolished by the addition of 
-aminocaproic acid.Binding of r-apo(a) and plasma-derivedLp(a) to Glu-plasminogen was assessed in solution using a mutantform of recombinant plasminogen[Plg(S741C)] labeled at the active site with5'-(iodoacetamido)fluorescein. High-affinity binding ofapo(a) to plasminogen was observed with the 17-kringle r-apo(a)(Kd = 20.1 ± 3.3 nM) as well aswithplasma-derived Lp(a) (Kd = 5.58 ± 0.08nM). Binding studies using various truncated and mutantformsof r-apo(a) demonstrated that sequences within apo(a) kringleIV types 2-9 and the strong lysine bindingsite (LBS) in apo(a) kringle IV type 10 are not required forhigh-affinity binding to plasminogen. In allcases, the binding stoichiometry for the apo(a)-plasminogeninteraction was determined to be 1:1. Bindingdata obtained using a 17-kringle r-apo(a) derivative lacking theprotease-like domain (17K
P; Kd =3158± 138 nM) indicate that sequences within the protease-like domain ofapo(a) mediate its interaction withLBS in plasminogen. We determined that r-apo(a) andplasminogen bind to distinct sites on plasmin-modified fibrinogen with the concentration of plasminogen binding sitesexceeding the concentration ofr-apo(a) sites by a factor of 10. Furthermore, r-apo(a)is capable of inhibiting the binding of plasminogento plasmin-modified fibrinogen surfaces, an effect which we show isattributable to the formation of asolution phase apo(a)/plasminogen complex which exhibits a greatlyreduced affinity for plasminogenbinding sites on plasmin-modified fibrinogen. The results of thisstudy provide new insights into themechanism by which apo(a) and Lp(a) may inhibit fibrinolysis,thus contributing to the atherothromboticrisk associated with this lipoprotein.
-aminocaproic acid.Binding of r-apo(a) and plasma-derivedLp(a) to Glu-plasminogen was assessed in solution using a mutantform of recombinant plasminogen[Plg(S741C)] labeled at the active site with5'-(iodoacetamido)fluorescein. High-affinity binding ofapo(a) to plasminogen was observed with the 17-kringle r-apo(a)(Kd = 20.1 ± 3.3 nM) as well aswithplasma-derived Lp(a) (Kd = 5.58 ± 0.08nM). Binding studies using various truncated and mutantformsof r-apo(a) demonstrated that sequences within apo(a) kringleIV types 2-9 and the strong lysine bindingsite (LBS) in apo(a) kringle IV type 10 are not required forhigh-affinity binding to plasminogen. In allcases, the binding stoichiometry for the apo(a)-plasminogeninteraction was determined to be 1:1. Bindingdata obtained using a 17-kringle r-apo(a) derivative lacking theprotease-like domain (17KP; Kd =3158± 138 nM) indicate that sequences within the protease-like domain ofapo(a) mediate its interaction withLBS in plasminogen. We determined that r-apo(a) andplasminogen bind to distinct sites on plasmin-modified fibrinogen with the concentration of plasminogen binding sitesexceeding the concentration ofr-apo(a) sites by a factor of 10. Furthermore, r-apo(a)is capable of inhibiting the binding of plasminogento plasmin-modified fibrinogen surfaces, an effect which we show isattributable to the formation of asolution phase apo(a)/plasminogen complex which exhibits a greatlyreduced affinity for plasminogenbinding sites on plasmin-modified fibrinogen. The results of thisstudy provide new insights into themechanism by which apo(a) and Lp(a) may inhibit fibrinolysis,thus contributing to the atherothromboticrisk associated with this lipoprotein.