High-Field EPR Spectroscopic Characterization of Mn(II) Bound to the Bacterial Solute-Binding Proteins MntC and PsaA
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Author(s)
Gagnon, Derek M.
Hadley, Rose Currier
Ozarowski, Andrew
Nolan, Elizabeth Marie
Britt, R. David
Date Issued
May 2019
Journal
Journal of Physical Chemistry B
Publisher
American Chemical Society (ACS)
Citation
Gagnon, Derek M. et al., "High-Field EPR Spectroscopic Characterization of Mn(II) Bound to the Bacterial Solute-Binding Proteins MntC and PsaA." Journal of Physical Chemistry B 123, 23 (June 2019): p. 4929–34 doi. 10.1021/acs.jpcb.9b03633 ©2019 Authors
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Author's final manuscript
Abstract
During infection, the bacterial pathogens Staphylococcus aureus and Streptococcus pneumoniae employ ATP-binding cassette (ABC) transporters to acquire Mn(II), an essential nutrient, from the host environment. Staphylococcal MntABC and streptococcal PsaABC attract the attention of the biophysical and bacterial pathogenesis communities because of their established importance during infection. Previous biophysical examination of Mn(II)-MntC and Mn(II)-PsaA using continuous-wave (≈9 GHz) electron paramagnetic resonance (EPR) spectroscopy revealed broad, difficult-to-interpret spectra (Hadley et al. J. Am. Chem. Soc. 2018, 140, 110-113). Herein, we employ high-frequency (>90 GHz), high-field (>3 T) EPR spectroscopy to investigate the Mn(II)-binding sites of these proteins and determine the spin Hamiltonian parameters. Our analyses demonstrate that the zero-field splitting (ZFS) is large for Mn(II)-MntC and Mn(II)-PsaA at +2.72 and +2.87 GHz, respectively. The measured 55Mn hyperfine coupling values for Mn(II)-MntC and Mn(II)-PsaA of 241 and 236 MHz, respectively, demonstrate a more covalent interaction between Mn(II) and the protein compared to Mn(II) in aqueous solution (≈265 MHz). These studies indicate that MntC and PsaA bind Mn(II) in a similar coordination geometry. Comparison of the ZFS values determined herein with those ascertained for other Mn(II) proteins suggests that the Mn(II)-MntC and Mn(II)-PsaA coordination spheres are not five-coordinate in solution. ©2019 American Chemical Society.
MIT Department
Massachusetts Institute of Technology. Department of Chemistry
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DOI of Published Version
https://doi.org/10.1021/ACS.JPCB.9B03633
