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The Solution Structure of CCL28 Reveals Structural Lability that Does Not Constrain Antifungal Activity. J Mol Biol 2018 09 14;430(18 Pt B):3266-3282

Date

06/19/2018

Pubmed ID

29913161

Pubmed Central ID

PMC6103841

DOI

10.1016/j.jmb.2018.06.001

Scopus ID

2-s2.0-85049041059   2 Citations

Abstract

The chemokine CCL28 is constitutively expressed in mucosal tissues and is abundant in low-salt mucosal secretions. Beyond its traditional role as a chemoattractant, CCL28 has been shown to act as a potent and broad-spectrum antimicrobial agent with particular efficacy against the commensal fungus and opportunistic pathogen Candida albicans. However, the structural features that allow CCL28 to perform its chemotactic and antimicrobial functions remain unknown. Here, we report the structure of CCL28, solved using nuclear magnetic resonance spectroscopy. CCL28 adopts the canonical chemokine tertiary fold, but also has a disordered C-terminal domain that is partially tethered to the core by a non-conserved disulfide bond. Structure-function analysis reveals that removal of the C-terminal tail reduces the antifungal activity of CCL28 without disrupting its structural integrity. Conversely, removal of the non-conserved disulfide bond destabilizes the tertiary fold of CCL28 without altering its antifungal effects. Moreover, we report that CCL28 unfolds in response to low pH but is stabilized by the presence of salt. To explore the physiologic relevance of the observed structural lability of CCL28, we investigated the effects of pH and salt on the antifungal activity of CCL28 in vitro. We found that low pH enhances the antifungal potency of CCL28, but also that this pH effect is independent of CCL28's tertiary fold. Given its dual role as a chemoattractant and antimicrobial agent, our results suggest that changes in the salt concentration or pH at mucosal sites may fine-tune CCL28's functional repertoire by adjusting the thermostability of its structure.

Author List

Thomas MA, He J, Peterson FC, Huppler AR, Volkman BF

Authors

Anna H. Huppler MD Assistant Professor in the Pediatrics department at Medical College of Wisconsin
Francis C. Peterson PhD Professor in the Biochemistry department at Medical College of Wisconsin
Brian F. Volkman PhD Professor in the Biochemistry department at Medical College of Wisconsin




MESH terms used to index this publication - Major topics in bold

Anti-Infective Agents
Candida albicans
Chemokines, CC
Humans
Hydrogen-Ion Concentration
Magnetic Resonance Spectroscopy
Models, Molecular
Protein Conformation
Protein Stability
Protein Unfolding
Salts
Solutions
Structure-Activity Relationship
Thermodynamics
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