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bioRxiv · 10.1101/776229

Faster diffusive dynamics of histone-like nucleoid structuring proteins in live bacteria caused by silver ions

Sadoon, A. A.·Khadka, P.·Freeland, J.·Gundampati, R. K.·Manso, R.·Ruiz, M.·Krishnamurthi, V. R.·Thallapuranam, S. K.·Chen, J.·Wang, Y.
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Abstract

The antimicrobial activity and mechanism of silver ions (Ag+) have gained broad attention in recent years. However, dynamic studies are rare in this field. Here, we report our measurement of the effects of Ag+ ions on the dynamics of histone-like nucleoid structuring (H-NS) proteins in live bacteria using single-particle tracking photoactivated localization microscopy (sptPALM). It was found that treating the bacteria with Ag+ ions led to faster diffusive dynamics of H-NS proteins. Several techniques were used to understand the mechanism of the observed faster dynamics. Electrophoretic mobility shift assay on purified H-NS proteins indicated that Ag+ ions weaken the binding between H-NS proteins and DNA. Isothermal titration calorimetry confirmed that DNA and Ag+ ions interact directly. Our recently developed sensing method based on bent DNA suggested that Ag+ ions caused dehybridization of double-stranded DNA (i.e., dissociation into single strands). These evidences led us to a plausible mechanism for the observed faster dynamics of H-NS proteins in live bacteria when subjected to Ag+ ions: Ag+-induced DNA dehybridization weakens the binding between H-NS proteins and DNA. This work highlighted the importance of dynamic study of single proteins in the live cells for understanding the functions of antimicrobial agents to the bacteria.

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Sadoon, A. A., Khadka, P., Freeland, J., Gundampati, R. K., Manso, R., Ruiz, M., Krishnamurthi, V. R., Thallapuranam, S. K., Chen, J., Wang, Y.. 2019-09-30. Faster diffusive dynamics of histone-like nucleoid structuring proteins in live bacteria caused by silver ions. https://doi.org/10.1101/776229

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