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High-Field EPR Spectroscopic Characterization of Mn(II) Bound to the Bacterial Solute-Binding Proteins MntC and PsaA

Derek M Gagnon1, Rose C Hadley2, Andrew Ozarowski3

  • 1Department of Chemistry , University of California Davis , Davis , California 95616 , United States.

The Journal of Physical Chemistry. B
|May 24, 2019
PubMed

Insights

Bacterial pathogens use manganese transporters MntABC and PsaABC to scavenge essential manganese (Mn(II)) during infection. High-field EPR reveals these transporters bind Mn(II) with a covalent interaction, suggesting a similar coordination geometry.

Area of Science:

  • Biophysics
  • Biochemistry
  • Microbiology

Background:

  • Bacterial pathogens like Staphylococcus aureus and Streptococcus pneumoniae utilize ATP-binding cassette (ABC) transporters to acquire manganese (Mn(II)).
  • The MntABC and PsaABC transporters are crucial for bacterial pathogenesis and are of significant interest to researchers.
  • Previous electron paramagnetic resonance (EPR) studies of Mn(II)-MntC and Mn(II)-PsaA yielded complex spectra, limiting detailed analysis.

Purpose of the Study:

  • To investigate the Mn(II)-binding sites within the MntABC and PsaABC transporters.
  • To determine the spin Hamiltonian parameters of Mn(II) bound to MntC and PsaA.
  • To elucidate the coordination geometry and metal-protein interactions within these essential transporters.

Main Methods:

  • Utilized high-frequency (>90 GHz) and high-field (>3 T) EPR spectroscopy.
  • Analyzed Mn(II)-MntC and Mn(II)-PsaA complexes.
  • Determined zero-field splitting (ZFS) and 55Mn hyperfine coupling values.

Main Results:

  • High-field EPR revealed large zero-field splitting (ZFS) values for Mn(II)-MntC (+2.72 GHz) and Mn(II)-PsaA (+2.87 GHz).
  • Measured 55Mn hyperfine coupling values (241 MHz for Mn(II)-MntC, 236 MHz for Mn(II)-PsaA) indicate a more covalent Mn(II)-protein interaction than in aqueous solution.
  • The data suggests MntC and PsaA bind Mn(II) in similar coordination environments.

Conclusions:

  • MntC and PsaA exhibit distinct Mn(II) coordination spheres compared to typical five-coordinate Mn(II) proteins.
  • The findings provide insights into the mechanism of Mn(II) uptake by essential bacterial transporters.
  • This research advances the understanding of metal ion acquisition strategies in bacterial pathogens.

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