Metal Exchange in the Interprotein ZnII -Binding Site of the Rad50 Hook Domain: Structural Insights into CdII -Induced DNA-Repair Inhibition.

Michał Padjasek,Maciej Pyrka,Michał Nowakowski,Maciej Maciejczyk,Artur Krężel,Olga Kerber,Wiktor Koźmiński

doi:10.1002/chem.201904942

Michał Padjasek, Maciej Pyrka + Show 5 more

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https://doi.org/10.1002/chem.201904942

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Abstract

CdII is a major genotoxic agent that readily displaces ZnII in a multitude of zinc proteins, abrogates redox homeostasis, and deregulates cellular metalloproteome. To date, this displacement has been described mostly for cysteine(Cys)‐rich intraprotein binding sites in certain zinc finger domains and metallothioneins. To visualize how a ZnII‐to‐CdII swap can affect the target protein's status and thus understand the molecular basis of CdII‐induced genotoxicity an intermolecular ZnII‐binding site from the crucial DNA repair protein Rad50 and its zinc hook domain were examined. By using a length‐varied peptide base, ZnII‐to‐CdII displacement in Rad50’s hook domain is demonstrated to alter it in a bimodal fashion: 1) CdII induces around a two‐orders‐of‐magnitude stabilization effect (log K12ZnII =20.8 vs. log K12CdII =22.7), which defines an extremely high affinity of a peptide towards a metal ion, and 2) the displacement disrupts the overall assembly of the domain, as shown by NMR spectroscopic and anisotropy decay data. Based on the results, a new model explaining the molecular mechanism of CdII genotoxicity that underlines CdII’s impact on Rad50’s dimer stability and quaternary structure that could potentially result in abrogation of the major DNA damage response pathway is proposed.

Highlights

Cadmium is a well-defined nephrotoxic, pneumotoxic, osteotoxic, and cardiotoxic agent and, on top of that, a strong carcinogen, a feature probably stemming from its extensive indirect genotoxicity.[1,2,3,4,5] Its detrimental effects on human health are known, but a clear mechanism connecting cadmium’s intake [b] Dr M
To assess if the structure and stability of CdII complexes rely on a similar structural basis to that of ZnII, we used a series of zinc hook (Hk) peptides ranging in length from 4 to 130 amino acid residues (Hk4– Hk130) (Figure 1)
The CdII ion is bound so tightly that it renders the zinc hook domain effectively blocked in one rigid conformation and incapable of any ZnII- or DNA damage response (DDR)-protein-driven structural rearrangements that seem to be crucial for the MR(N/X) complex’s multifunctionality

Summary

Introduction

Cadmium is a well-defined nephrotoxic, pneumotoxic, osteotoxic, and cardiotoxic agent and, on top of that, a strong carcinogen, a feature probably stemming from its extensive indirect genotoxicity.[1,2,3,4,5] Its detrimental effects on human health are known, but a clear mechanism connecting cadmium’s intake [b] Dr M. Pyrka Department of Physics and Biophysics Faculty of Food Science University of Warmia and Mazury in Olsztyn Oczapowskiego 4, 10-719 Olsztyn (Poland).

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