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A knottin scaffold directs the CXC-chemokine-binding specificity of tick evasins

Lookup NU author(s): Professor Akane KawamuraORCiD

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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).

Abstract

© 2019 American Society for Biochemistry and Molecular Biology Inc. All rights reserved.Tick evasins (EVAs) bind either CC- or CXC-chemokines by a poorly understood promiscuous or "one-to-many" mechanism to neutralize inflammation. Because EVAs potently inhibit inflammation in many preclinical 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- CXCchemokines, in several cases including CXC-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 antiparallel β-sheet with six conserved cysteine residues forming a disulfide-bonded knottin scaffold that creates a contiguous solvent-accessible surface. Swapping analyses identified distinct knottin scaffold segments necessary for different CXCchemokine- 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 CXCchemokine- binding tick EVAs achieve class specificity but also engage in promiscuous binding.

Publication metadata

Author(s): Lee AW, Deruaz M, Lynch C, Davies G, Singh K, Alenazi Y, Eaton JRO, Kawamura A, Shaw J, Proudfoot AEI, Dias JM, Bhattacharya S

Publication type: Article

Publication status: Published

Journal: Journal of Biological Chemistry

Year: 2019

Volume: 294

Issue: 29

Pages: 11199-11212

Print publication date: 19/07/2019

Online publication date: 05/06/2019

Acceptance date: 25/05/2019

Date deposited: 10/10/2019

ISSN (print): 0021-9258

ISSN (electronic): 1083-351X

Publisher: American Society for Biochemistry and Molecular Biology Inc.

URL: https://doi.org/10.1074/jbc.RA119.008817

DOI: 10.1074/jbc.RA119.008817

PubMed id: 31167786

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