Move Over, DNA

by Merry Youle
 

For 50 years, researchers have  mulled over why D. radiodurans is able to survive 100 times more ionizing radiation (IR) than other bacteria, 2000 times more than a human being. Although both DNA and proteins are damaged by IR, DNA was widely regarded as the critical target. That D. ra­diodurans can suffer 100 double strand DNA breaks per genome suggests an extraordinary DNA repair mechanism. Alas, such a mechanism has not been found.
 

Two cells of D. radiodurans  showing the distribution of iron (red line) and man­ganese (turquoise, purple, blue, and green lines indicating increasing con­cen­trations). Source

Attention shifted in 2004 when Daly et al. reported that the most IR-resistant bacteria had 300 times more man­ganese and three times less iron than the most IR-sen­sitive ones.
 

Their recent study demonstrates that these minerals pro­tect proteins, not DNA, from IR-induced oxidative dam­age. Lower the intracellular manganese content and the cells become sensitive to protein oxidation and radiation damage. The researchers postulated that manganese ions transform damaging superoxide radicals (which can't easily cross the cell membrane) into hydrogen per­oxide, which can be excreted. Indeed, resistant cells ex­crete peroxide following radiation exposure.
 

The moral of this story?  Protect your proteins and your DNA will take care of itself.

 

 

 

 

Comments

Very, Very interesting summary!