As Selectively Induces a Disorder-to-Order Transition in the Metalloid Binding Region of the AfArsR Protein.

Arsenic is highly toxic and a significant threat to human health, but certain bacteria have developed defense mechanisms initiated by As binding to As-sensing proteins of the ArsR family. The transcriptional regulator AfArsR responds to As and Sb by coordinating the metalloids with three cysteines, located in a short sequence of the same monomer chain. Here, we characterize the binding of As and Hg to a model peptide encompassing this fragment of the protein via solution equilibrium and spectroscopic/spectrometric techniques (pH potentiometry, UV, CD, NMR, PAC, EXAFS, and ESI-MS) combined with DFT calculations and MD simulations.

Inducing α-Helicity in Peptides by Silver Coordination to Cysteine.

Short peptide sequences consisting of two cysteine residues separated by three other amino acids display complete change from random coil to α-helical secondary structure in response to addition of Ag ions. The folded CXXXC/Ag complex involves formation of multinuclear Ag species and is stable in a wide pH range from below 3 to above 8. The complex is stable through reversed-phase HPLC separation as well as towards a physiological level of chloride ions, based on far-UV circular dichroism spectroscopy.

Revisiting the hydrolysis of ampicillin catalyzed by Temoneira-1 β-lactamase, and the effect of Ni(II), Cd(II) and Hg(II).

β-Lactamases grant resistance to bacteria against β-lactam antibiotics. The active center of TEM-1 β-lactamase accommodates a Ser-Xaa-Xaa-Lys motif. TEM-1 β-lactamase is not a metalloenzyme but it possesses several putative metal ion binding sites.

Tristhiolato Pseudopeptides Bind Arsenic(III) in an AsS Coordination Environment Imitating Metalloid Binding Sites in Proteins.

The As binding of two NTA-based tripodal pseudopeptides, possessing three cysteine (ligand ) or d-penicillamine residues (ligand ) as potential coordinating groups for soft semimetals or metal ions, was studied by experimental (UV, CD, NMR, and ESI-MS) and theoretical (DFT) methods. All of the experimental data, obtained with the variation of the As:ligand concentration ratios or pH values in some instances, evidence the exclusive formation of species with an AsS-type coordination mode. The UV-monitored titration of the ligands with arsenous acid at pH = 7.

Magnesium(II)-ATP Complexes in 1-Ethyl-3-Methylimidazolium Acetate Solutions Characterized by Mg β-Radiation-Detected NMR Spectroscopy.

The complexation of Mg with adenosine 5'-triphosphate (ATP) is omnipresent in biochemical energy conversion, but is difficult to interrogate directly. Here we use the spin- β-emitter Mg to study Mg -ATP complexation in 1-ethyl-3-methylimidazolium acetate (EMIM-Ac) solutions using β-radiation-detected nuclear magnetic resonance (β-NMR). We demonstrate that (nuclear) spin-polarized Mg, following ion-implantation from an accelerator beamline into EMIM-Ac, binds to ATP within its radioactive lifetime before depolarizing.