Insight into the interaction between thrombin and the Anopheles gambiae salivary intrinsically disordered protein cE5.

Anopheles mosquitoes are vectors of malaria, a potentially fatal infectious disease affecting more than half a billion people worldwide. Malaria is caused by Plasmodium spp. parasites that infect liver and red blood cells, and it is transmitted exclusively through the bites of Anopheles mosquitoes. These blood-feeding insects include in their salivary antihemostatic arsenal a potent thrombin inhibitor, the flexible and cysteine-less polypeptide anophelin. Anopheles gambiae is the primary vector of malaria in sub-Saharan Africa and its anophelin family member, named cE5, was previously expressed in recombinant form and shown to be a highly specific, tight- and fast-binding dual inhibitor of thrombin. The setting up of conditions for large-scale expression and purification of the cE5 protein paved the way for structural studies, which may shed further light not only on the mechanism of thrombin inhibition by anophelin family members but also on the design of novel antithrombotics. A structural characterization by means of circular dichroism (CD) studies, NMR spectroscopy, homology modeling and ITC experiments has been performed on cE5 and on its interaction with thrombin. All the results will be widely discussed.