Breakthrough study sheds light on cell defense against radiation exposure

The study is entitled, "Responses of Mn2+ Speciation in Deinococcus radiodurans and Escherichia coli to Gamma-Radiation by Advanced Paramagnetic Resonance Methods," and published in the March 25 edition of the Proceedings of the National Academy of Sciences.

The collaborative study was led by Michael J. Daly, Ph.D., professor at the Uniformed Services University of the Health Sciences (USU), Department of Pathology, and Brian Hoffman, Ph.D., professor at Northwestern University, Department of Chemistry, and reveals the structure of manganese-based chemical antioxidants in Deinococcus radiodurans. The bacterium can survive massive exposures to gamma-radiation, ultraviolet radiation, and other agents which kill cells by generating dangerous oxygen radicals. The advanced spectroscopy techniques applied shed light on how Deinococcus Mn complexes defend cells from radiation, and how to better harness their potent antioxidant properties for practical purposes.

Daly's team previously reported that D. radiodurans accomplishes its astonishing survival feats in an unexpected way -- by shielding its enzymes from oxidative damage using a mechanism which involves divalent Mn ions (Mn2+). This form of protection spares its DNA repair enzymes from radiation damage and allows the cells to reassemble their broken genomes with extraordinary efficiency. The current study shows that most Mn2+ in D. radiodurans cells is partnered with small nitrogenous compounds and inorganic phosphate, which form complexes that are impressively radioprotective. Following exposure to gamma-radiation, great differences were observed in the responses of Mn2+ complexes in D. radiodurans and Mn2+ complexes in radiation-sensitive bacteria -- information which was used to identify the building blocks and structure of Mn2+ complexes as they exist in living D. radiodurans cells. The work represents a blueprint for synthesizing Deinococcus Mn complexes in the laboratory, with the prospect of developing new pharmaceutical interventions to combat oxidative stress in diverse settings, including the preparation of irradiated vaccines, during radiotherapy, against ultraviolet rays during sunbathing, and aging.