Rojas Masyelly, Labrador Indira, Concepción Juan L, Aldana Elis, Avilan Luisana
Laboratorio de Fisiología, Facultad de Ciencias, Universidad de Los Andes, Mérida 5101, Venezuela.
Acta Trop. 2008 Jul;107(1):54-8. doi: 10.1016/j.actatropica.2008.04.013. Epub 2008 Apr 22.
The binding constants of the interaction between plasminogen and Trypanosoma cruzi epimastigotes were determined. An indirect method in which the bound plasminogen is detached from the cell by epsilon-aminocaproic acid and a direct method through biotinylated plasminogen were used. The analyses revealed a dissociation constant (Kd) from 0.4 to 1.2microM, these values being compatible with recognition in vivo. Moreover, epimastigotes from the gut of Rhodnius prolixus were able to bind plasminogen from the blood meal. Fragments derived from elastase digestion of plasminogen were tested for their ability to bind T. cruzi cells. The fragment with highest ability to interact with the parasite was miniplasminogen that bound in a concentration-dependent and saturable manner with a Kd similar to that for plasminogen. This binding was inhibited by epsilon-aminocaproic acid indicating that the lysine-binding site of kringle 5 may be responsible for the interaction of plasminogen with T. cruzi.
测定了纤溶酶原与克氏锥虫前鞭毛体之间相互作用的结合常数。采用了一种间接方法，即通过ε-氨基己酸将结合的纤溶酶原从细胞上分离下来，以及一种通过生物素化纤溶酶原的直接方法。分析显示解离常数（Kd）为0.4至1.2微摩尔，这些值与体内识别情况相符。此外，来自红带锥蝽肠道的前鞭毛体能够结合来自血餐中的纤溶酶原。测试了纤溶酶原经弹性蛋白酶消化产生的片段与克氏锥虫细胞结合的能力。与寄生虫相互作用能力最强的片段是微型纤溶酶原，它以浓度依赖且可饱和的方式结合，其Kd与纤溶酶原相似。这种结合受到ε-氨基己酸的抑制，表明kringle 5的赖氨酸结合位点可能是纤溶酶原与克氏锥虫相互作用的原因。
