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Specific Histidine Residues Confer Histatin Peptides with Copper-Dependent Activity against Candida albicans
Abstract
The histidine-rich salivary peptides of the histatin family are known to bind copper
(Cu) and other metal ions in vitro; however, the details of these interactions are
poorly understood, and their implications for in vivo antifungal activity have not
been established. Here, we show that the availability of Cu during exposure of Candida
albicans to histatin-5 (Hist-5) modulates its antifungal activity. Antifungal susceptibility
testing revealed that co-treatment of Hist-5 with Cu improved the EC50 from ∼5 to
∼1 μM, whereas co-treatment with a high-affinity Cu-specific chelator abrogated antifungal
activity. Spectrophotometric titrations revealed two previously unrecognized Cu(I)-binding
sites with apparent Kd values at pH 7.4, ∼20 nM, and confirmed a high-affinity Cu(II)-binding
site at the Hist-5 N-terminus with an apparent Kd of ∼8 pM. Evaluation of a series
of His-to-Ala full-length and truncated Hist-5 peptides identified adjacent His residues
(bis-His) as critical anchors for Cu(I) binding, with the presence of a third ligand
revealed by X-ray absorption spectroscopy. On their own, the truncated peptides were
ineffective at inhibiting the growth of C. albicans, but treatment with supplemental
Cu resulted in EC50 values down to ∼5 μM, approaching that of full-length Hist-5.
The efficacy of the peptides depended on an intact bis-His site and correlated with
Cu(I) affinity. Together, these results establish new structure–function relationships
linking specific histidine residues with Cu binding affinity and antifungal activity
and provide further evidence of the involvement of metals in modulating the biological
activity of these antifungal peptides.
Type
Journal articlePermalink
https://hdl.handle.net/10161/15179Published Version (Please cite this version)
10.1021/acs.biochem.7b00348Publication Info
Conklin, SE; Bridgman, EC; Su, Q; Riggs-Gelasco, P; & Franz, KJ (2017). Specific Histidine Residues Confer Histatin Peptides with Copper-Dependent Activity
against Candida albicans. Biochemistry. 10.1021/acs.biochem.7b00348. Retrieved from https://hdl.handle.net/10161/15179.This is constructed from limited available data and may be imprecise. To cite this
article, please review & use the official citation provided by the journal.
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Show full item recordScholars@Duke
Steven Conklin
Student
Steven E. Conklin is originally from Guaynabo, Puerto Rico and graduated from the
University of Puerto Rico – Río Piedras Campus in 2013 with a B.S. in
Chemistry. Currently, he is a Chemistry Ph.D. candidate working in Katherine J. Franz’s
laboratory, which focuses on bioinorganic chemistry.
Katherine J. Franz
Chair of the Department of Chemistry
Research in the Franz group is involved in elucidating the structural and functional
consequences of metal ion coordination in biological systems. We are particularly
interested in understanding the coordination chemistry utilized by biology to manage
essential yet toxic species like copper and iron. Understanding these principles
further guides our development of new chemical tools to manipulate biological metal
ion location, speciation, and reactivity for potential therapeutic benefit. We use
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