Structural and biochemical characterization of the novel serpin Iripin-5 from Ixodes ricinus

Iripin-5 is the main Ixodes ricinus salivary serpin, which acts as a modulator of host defence mechanisms by impairing neutrophil migration, suppressing nitric oxide production by macrophages and altering complement functions. Iripin-5 influences host immunity and shows high expression in the salivary glands. Here, the crystal structure of Iripin-5 in the most thermodynamically stable state of serpins is described. In the reactive-centre loop, the main substrate-recognition site of Iripin-5 is likely to be represented by Arg342, which implies the targeting of trypsin-like proteases. Furthermore, a computational structural analysis of selected Iripin-5-protease complexes together with interface analysis revealed the most probable residues of Iripin-5 involved in complex formation.

Automated summary

Iripin-5, the main serpin in Ixodes ricinus saliva, modulates host defense mechanisms by affecting neutrophil migration, macrophage nitric oxide production, and complement functions. The crystal structure of Iripin-5 in its most stable state reveals a potential substrate-recognition site at Arg342 in the reactive-centre loop. Computational analysis of Iripin-5-protease complexes also identifies the most likely residues involved in complex formation.