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 cystei ne, indicating that early arrest of protein synthesis previously obser ved in such a system was due to oxygen starvation in the reaction mixt ure. This hypothesis was confirmed since the amount of proteins synthe sized 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 stimulati on could be due to a common property between both molecules: the oxidi zing 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 radic al scavengers. These experiments suggest that the superoxide radical p lays an important role in in vitro translation.