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Responses of Mn2+ speciation in Deinococcus radiodurans and Escherichia coil to γ-radiation by advanced paramagnetic resonance methods.

Authors :
Sharma, Ajay
Gaidamakova, Elena K.
Matrosova, Vera Y.
Bennett, Brian
Daly, Michael J.
Hoffman, Brian M.
Source :
Proceedings of the National Academy of Sciences of the United States of America; 4/9/2013, Vol. 110 Issue 15, p5945-5950, 6p
Publication Year :
2013

Abstract

The remarkable ability of bacterium Deinococcus radiodurans to survive extreme doses of γ-rays (12,000 Gy), 20 times greater than Escherichia coli, is undiminished by loss of Mn-dependent superoxide dismutase (SodA). D. radiodurans radiation resistance is attributed to the accumulation of low-molecular-weight (LMW) "antioxidant" Mn<superscript>2+</superscript>-metabolite complexes that protect essential enzymes from oxidative damage. However, in vivo information about such complexes within D. radiodurans cells is lacking, and the idea that they can supplant reactive-oxygen-species (ROS)-scavenging enzymes remains controversial. In this report, measurements by advanced paramagnetic resonance techniques [electron-spin-echo (ESE)-EPR/electron nuclear double resonance/ ESE envelope modulation (ESEEM)] reveal differential details of the in vivo Mn<superscript>2+</superscript> speciation in D. radiodurans and E. coli cells and their responses to 10 kGy γ-irradiation. The Mn<superscript>2+</superscript> of D. radiodurans exists predominantly as LMW complexes with nitrogenous metabolites and orthophosphate, with negligible EPR signal from Mn<superscript>2+</superscript> of SodA. Thus, the extreme radiation resistance of D. radiodurans cells cannot be attributed to SodA. Correspondingly, 10 kGy irradiation causes no change in D. radiodurans Mn<superscript>2+</superscript> speciation, despite the paucity of holo-SodA. In contrast, the EPR signal of E. coli is dominated by signals from low-symmetry enzyme sites such as that of SodA, with a minority pool of LMW Mn<superscript>2+</superscript> complexes that show negligible coordination by nitrogenous metabolites. Nonetheless, irradiation of E. coli majorly changes LMW Mn<superscript>2+</superscript> speciation, with extensive binding of nitrogenous ligands created by irradiation. We infer that E. coli is highly susceptible to radiation- induced ROS because it lacks an adequate supply of LMW Mn antioxidants. [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
00278424
Volume :
110
Issue :
15
Database :
Complementary Index
Journal :
Proceedings of the National Academy of Sciences of the United States of America
Publication Type :
Academic Journal
Accession number :
86939378
Full Text :
https://doi.org/10.1073/pnas.1303376110