Characterizing the conformational dynamics of metal-free PsaA using molecular dynamics simulations and electron paramagnetic resonance spectroscopy

Evelyne Deplazes, Stephanie L. Begg, Jessica H. Van Wonderen, Rebecca Campbell, Bostjan Kobe, James C. Paton, Fraser MacMillan, Christopher A. McDevitt, Megan L. O'Mara

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)
9 Downloads (Pure)


Prokaryotic metal-ion receptor proteins, or solute-binding proteins, facilitate the acquisition of metal ions from the extracellular environment. Pneumococcal surface antigen A (PsaA) is the primary Mn2+-recruiting protein of the human pathogen Streptococcus pneumoniae and is essential for its in vivo colonization and virulence. The recently reported high-resolution structures of metal- free and metal-bound PsaA have provided the first insights into the mechanism of PsaA-facilitated metal binding. However, the conformational dynamics of metal-free PsaA in solution remain unknown. Here, we use continuous wave electron paramagnetic resonance (EPR) spectroscopy and molecular dynamics (MD) simulations to study the relative flexibility of the structural domains in metal-free PsaA and its distribution of conformations in solution. The results show that the crystal structure of the metal-free PsaA is a good representation of the dominant conformation in solution, but the protein also samples structurally distinct conformations that are not captured by the crystal structure. Further, these results suggest that the metal binding site is larger and more solvent exposed than indicated by the metal-free crystal structure. Collectively, this study provides atomic-resolution insight into the conformational dynamics of PsaA prior to metal binding and lays the groundwork for future EPR and MD based studies of PsaA in solution.
Original languageEnglish
Pages (from-to)51-60
Number of pages10
JournalBiophysical Chemistry
Early online date3 Sep 2015
Publication statusPublished - Dec 2015


  • Cluster A-I solute-binding protein (SBP)
  • Streptococcus pneumoniae
  • PsaA
  • Molecular dynamics simulations
  • Electron paramagnetic resonance (EPR) spectroscopy
  • Protein flexibility
  • Spin-label mobility

Cite this