The diphtheria toxin repressor (DtxR) is an Fe(II)-activated transcriptional regulator of iron homeostatic and virulence genes in Corynebacterium diphtheriae. DtxR is a two-domain protein that contains two structurally and functionally distinct metal binding sites. Here, we investigate the molecular steps associated with activation by Ni(II)Cl(2) and Cd(II)Cl(2). Equilibrium binding energetics for Ni(II) were obtained from isothermal titration calorimetry, indicating apparent metal dissociation constants of 0.2 and 1.7 microM for two independent sites. The binding isotherms for Ni(II) and Cd(II) exhibited a characteristic exothermic-endothermic pattern that was used to infer the metal binding sequence by comparing the wild-type isotherm with those of several binding site mutants. These data were complemented by measuring the distance between specific backbone amide nitrogens and the first equivalent of metal through heteronuclear NMR relaxation measurements. Previous studies indicated that metal binding affects a disordered to ordered transition in the metal binding domain. The coupling between metal binding and structure change was investigated using near-UV circular dichroism spectroscopy. Together, the data show that the first equivalent of metal is bound by the primary metal binding site. This binding orients the DNA binding helices and begins to fold the N-terminal domain. Subsequent binding at the ancillary site completes the folding of this domain and formation of the dimer interface. This model is used to explain the behavior of several mutants.
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Dalton Trans
December 2024
Institut für Chemie, Humboldt-Universität zu Berlin, Brook-Taylor-Str. 2, 12489 Berlin, Germany.
We report the proton-coupled electron transfer (PCET) reactivity of an octahedral Ta(V) aniline complex supported by an acridane-derived redox active NNN pincer ligand. The reversible binding of aniline to a Ta(V) dichloride induces significant coordination-induced bond weakening (CIBW) of the aniline N-H bonds. This enables a rare two-fold hydrogen atom abstraction, resulting in a terminal imido complex and a two-electron oxidation of the NNN pincer ligand, all while maintaining the metal's oxidation state.
View Article and Find Full Text PDFInt J Biol Macromol
December 2024
College of Food Science and Engineering, Ningbo University, Ningbo, Zhejiang 315211, China. Electronic address:
The influence of metal elements on the biomedical activity of microalgal exopolysaccharides (EPS) remains underexplored. This study examined the antitumor properties of Botryococcus braunii EPS under high cobalt conditions and the role of exogenous 3-indole acetic acid (IAA) in enhancing its activity. Results showed that IAA mitigated cobalt-induced inhibition of B.
View Article and Find Full Text PDFInorg Chem
December 2024
Department of Chemistry, University of Kansas, 1567 Irving Hill Road, Lawrence, Kansas 66045, United States.
Both cyclic "crown" and acyclic "tiara" polyethers have been recognized as useful for the binding of metal cations and enabling the assembly of multimetallic complexes. However, the properties of heterobimetallic complexes built upon acyclic polyethers have received less attention than they deserve. Here, the synthesis and characterization of a family of eight redox-active heterobimetallic complexes that pair a nickel center with secondary redox-inactive cations (K, Na, Li, Sr, Ca, Zn, La, and Lu) bound in acyclic polyether "tiara" moieties are reported.
View Article and Find Full Text PDFAcc Chem Res
December 2024
Department of Chemical and Petroleum Engineering, University of Kansas, Lawrence, Kansas 66045, United States.
ConspectusThe surface of a catalyst is crucial for understanding the mechanisms of catalytic reactions at the molecular level and developing new catalysts with higher activity, selectivity, and durability. Ambient pressure X-ray photoelectron spectroscopy (AP-XPS) is a technique studying the surface of a sample in the gas phase, mainly identifying chemical identity, analyzing oxidation state, and measuring surface composition.In the last decade, numerous photoelectron spectroscopic methods for fundamental studies of key topics in catalysis using AP-XPS have been developed.
View Article and Find Full Text PDFChem Asian J
December 2024
University of Oklahoma, Chemistry and Biochemistry, 101 Stephenson Pkwy, Room 3310, 73019, Norman, UNITED STATES OF AMERICA.
Proton-coupled electron transfer (PCET) reactions are fundamental to energy storage and conversion processes. By coupling electrons with protons, the net charge neutrality is retained, preventing electrode decomposition due to charge imbalance. PCET reactions with equimolar amounts of protons and electrons can be considered as a net H-atom transfer (HAT) reaction.
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