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In biological systems, chemical and physical transformations of engineered silver nanomaterials (AgENMs) are mediated, in part, by proteins and other biomolecules. Metalloprotein interactions with AgENMs are also central in understanding toxicity, antimicrobial, and resistance mechanisms. Despite their readily available thiolate and amine ligands, zinc finger (ZF) peptides have thus far escaped study in reaction with AgENMs and their Ag( i ) oxidative dissolution product. We report spectroscopic studies that characterize AgENM and Ag( i ) interactions with two ZF peptides that differ in sequence, but not in metal binding ligands: the ZF consensus peptide CP-CCHC and the C-terminal zinc finger domain of HIV-1 nucleocapsid protein p7 (NCp7_C). Both ZF peptides catalyze AgENM (10 and 40 nm, citrate coated) dissolution and agglomeration, two important AgENM transformations that impact bioreactivity. AgENMs and their oxidative dissolution product, Ag( i )(aq), mediate changes to ZF peptide structure and metalation as well. Spectroscopic titrations of Ag( i ) into apo-ZF peptides show an Ag( i )–thiolate charge transfer band, indicative of Ag( i )–ZF binding. Fluorescence studies of the Zn( ii )–NCp_7 complex indicate that the Ag( i ) also effectively competes with the Zn( ii ) to drive Zn( ii ) displacement from the ZFs. Upon interaction with AgENMs, Zn( ii ) bound ZF peptides show a secondary structural change in circular dichroism spectroscopy toward an apo-like structure. The results suggest that Ag( i ) and AgENMs may alter ZF protein function within the cell.
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Iron–Sulfur Clusters in Zinc Finger Proteins
Zinc finger (ZF) proteins are proteins that use zinc as a structural cofactor. The common feature among all ZFs is that they contain repeats of four cysteine and/or histidine residues within their primary amino acid sequence. With the explosion of genome sequencing in the early 2000s, a large number of proteins were annotated as ZFs based solely upon amino acid sequence. As these proteins began to be characterizedexperimentally, it was discovered that some of these proteins contain iron–sulfur sites either in place of or in addition to zinc. Here, we describe methods to isolate and characterize one such ZF protein, cleavage and polyadenylation specificity factor 30 (CPSF3O) with respect to its metal-loading and RNA-binding activity.
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- Award ID(s):
- 1708732
- PAR ID:
- 10065273
- Date Published:
- Journal Name:
- Methods in enzymology
- Volume:
- 599
- ISSN:
- 1557-7988
- Page Range / eLocation ID:
- 101-137
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1016/bs.mie.2017.09.005
