1. As III Selectively Induces a Disorder-to-Order Transition in the Metalloid Binding Region of the AfArsR Protein.
- Author
-
Tóth A, Sajdik K, Gyurcsik B, Nafaee ZH, Wéber E, Kele Z, Christensen NJ, Schell J, Correia JG, Sigfridsson Clauss KGV, Pittkowski RK, Thulstrup PW, Hemmingsen L, and Jancsó A
- Subjects
- Binding Sites, Bacterial Proteins chemistry, Bacterial Proteins metabolism, Metalloids chemistry, Metalloids metabolism, Density Functional Theory, Molecular Dynamics Simulation, Protein Binding, Arsenic chemistry, Arsenic metabolism
- Abstract
Arsenic is highly toxic and a significant threat to human health, but certain bacteria have developed defense mechanisms initiated by As
III binding to AsIII -sensing proteins of the ArsR family. The transcriptional regulator AfArsR responds to AsIII and SbIII by coordinating the metalloids with three cysteines, located in a short sequence of the same monomer chain. Here, we characterize the binding of AsIII and HgII 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. Coordination of AsIII changes the peptide structure from a random-coil to a well-defined structure of the complex. A trigonal pyramidal AsS3 binding site is formed with almost exactly the same structure as observed in the crystal structure of the native protein, implying that the peptide possesses all of the features required to mimic the AsIII recognition and response selectivity of AfArsR. Contrary to this, binding of HgII to the peptide does not lead to a well-defined structure of the peptide, and the atoms near the metal binding site are displaced and reoriented in the HgII model. Our model study suggests that structural organization of the metal site by the inducer ion is a key element in the mechanism of the metalloid-selective recognition of this protein.- Published
- 2024
- Full Text
- View/download PDF