STIMULATION OF TRANSLATION BY REACTIVE OXYGEN SPECIES IN A CELL-FREE SYSTEM

Wheat germ lysate was used as a model system for in vitro translation. We show that an increase of the exchange surface between the reaction mixture and the atmosphere enhanced the amount of incorporated cysteine, indicating that early arrest of protein synthesis previously observed in such a system was due to oxygen starvation in the reaction mixture. This hypothesis was confirmed since the amount of proteins synthesized and the rate of translation increased when oxygen was added. We show that an addition of hydrogen peroxide to the translation mixture had the same effect as oxygen, allowing us to postulate that stimulation could be due to a common property between both molecules: the oxidizing behaviour. Free radicals in in vitro translation were believed to be involved since the utilization of iron chelating agents inhibited translation. This hypothesis was emphasized by the positive effect of a free radical generating system and the negative effect of free radical scavengers. These experiments suggest that the superoxide radical plays an important role in in vitro translation.