Selective coordination of cobalt ions by zinc fingers in Escherichia coli

Abstract

The ability of peptides to coordinate with specific metal ions is crucial for environmental protection and recycling processes, because of the toxicity and scarcity of the ions. One-third of proteins in biological systems have binding affinities to specific metal ions, and thus, can be further applied to collect precious metal ions. Zinc ion is a necessary co-factor for the regulation of physiological responses in biological systems, because of its ability to bind biomolecules. In this study, three zinc finger (ZF) domains (PARIS_ZF2-4) from Parkin-interacting substrates (PARIS) were used to harvest heterometals such as Co 2+ , Cu 2+ , and Fe 3+ in Escherichia coli. Spectroscopic results demonstrated that PARIS_ZF2-4 can coordinate with Co 2+ during expression. Purified PARIS_ZF2-4 generated specific d-d transition bands (570 and 644 nm), which were monitored upon the addition of Co 2+ to apo-PARIS_ZF2-4. These results can facilitate the possible applications of the ZF domain in heterometal substitution and elimination in biological systems.

Decoding the Parkinson’s Symphony: PARIS, Maestro of Transcriptional Regulation and Metal Coordination for Dopamine Release

“…573 and 643 nm corresponding to d–d transitions were monitored, similar to those from the classical ZF domains, such as zinc interacting factor-268 (ZIF268) . Thus, the d–d Abs patterns observed in the Co­(II)–PARIS­(ZF2–4) complex suggest that the Co­(II) center is surrounded by PARIS­(ZF2–4), imparting a tetrahedral geometry that is typically detected in classical ZF domains. , …”

“…Curve-fitting based on the d–d transition suggested that the K d of Co­(II) from apo-PARIS­(ZF2–4) was (49.1 ± 7.7) × 10 –9 M (Figure A). This value varies from those of the other ZF domains because the general K d value is in the micromolar range. ,, This phenomenon can be explained by the effect of Co­(II) substitution in E. coli . After the addition of 100 μM cobalt, the E. coli expressed PARIS­(ZF2–4) coordinated with Co­(II), and this outcome was not detected in the case of other metal ions, including Cu­(II) and Fe­(III).…”

“…Parkin interacting substrate (PARIS, zinc finger protein 746) is a transcriptional regulator with diverse ZF domains that facilitate intricate interactions with its binding partners (Figures A,B and S1). − The N-terminus harbors a Krüppel-associated box (KRAB), whereas the C-terminus contains one nonclassical (Cys 2 HisCys) and three classical (Cys 2 His 2 ) ZF domains. Given that the biological levels of PARIS are adjusted by the ubiquitin-proteasome pathway via binding to and ubiquitination by the E3 ubiquitin ligase parkin, the accumulation of PARIS and its subsequent functions as a transcriptional repressor toward peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) can ensue in parkin-inactivated systems (Figure C). ,, Since PGC-1α regulates the transcription of several genes critical for various metabolic activities, , the aberrant expression of PARIS could contribute to pathological consequences through the interactions between PARIS and the insulin response sequence (IRS; Figures D and S2) in the PGC-1α promoter. , Previous studies have proposed that the specific nucleotide sequence 5′-TATTTT­(T/G) in the IRS is the mediator of such interactions; , however, the details of the binding events and biophysical properties of the modular ZF domains within PARIS remain unclear.…”

“…For metal-binding studies, apo-PARIS­(ZF2–4) was prepared via acid treatment to eliminate metal ions (Figure S3B). The electronic absorption (Abs) spectrum demonstrated that apo-ZF domains lose coordination to Zn­(II) and the purified PARIS­(ZF2–4) coordinated to Zn­(II). , …”

“…The metal binding ability of PARIS­(ZF2–4) in E. coli can be explained through these observations: The cobalt ion in the PARIS­(ZF2–4) expressed in the presence of higher cobalt ion concentration can replace the zinc ions owing to the relatively low association . During the expression of PARIS­(ZF2–4) using IPTG in HIT cells, the newly synthesized ZF domains were exposed to cobalt-rich environments, which induced the formation of the Co­(II)–PARIS­(ZF2–4) complex.…”