Cookies on this website
We use cookies to ensure that we give you the best experience on our website. If you click 'Continue' we'll assume that you are happy to receive all cookies and you won't see this message again. Click 'Find out more' for information on how to change your cookie settings.
Skip to main content

Tick evasins (EVAs) bind either CC or CXC-chemokines by a poorly understood promiscuous or "one-to-many" mechanism to neutralize inflammation. Since EVAs potently inhibit inflammation in many pre-clinical models, highlighting their potential as biological therapeutics for inflammatory diseases, we sought to further unravel the CXC-chemokine-EVA interactions. Using yeast surface display, we identified and characterized 27 novel CXC-chemokine-binding evasins homologous to EVA3 and defined two functional classes. The first, which included EVA3, exclusively bound ELR+ CXC-chemokines, whereas the second class bound both ELR+ and ELR- CXC-chemokines, in several cases including C-X-C motif chemokine ligand 10 (CXCL10), but, surprisingly, not CXCL8. The X-ray crystal structure of EVA3 at a resolution of 1.79 Å revealed a single anti-parallel b-sheet with six conserved cysteine residues forming a disulfide-bonded knottin scaffold which creates a contiguous solvent-accessible surface. Swapping analyses identified distinct knottin scaffold segments necessary for different CXC-chemokine-binding activities, implying that differential ligand positioning, at least in part, plays a role in promiscuous binding. Swapping segments also transferred chemokine-binding activity, resulting in a hybrid EVA with dual CXCL10- and CXCL8-binding activities. The solvent-accessible surfaces of the knottin scaffold segments have distinctive shape and charge, which we suggest drives chemokine binding specificity. These studies provide structural and mechanistic insight into how CXC-chemokine-binding tick EVAs achieve class specificity but also engage in promiscuous binding.

Original publication

DOI

10.1074/jbc.RA119.008817

Type

Journal article

Journal

J Biol Chem

Publication Date

05/06/2019

Keywords

chemokine, chemotaxis, crystal structure, evasin, host-pathogen interaction, immune response, inflammation, knottin, protein-protein interaction, tick