Photodynamic action of thiopyronine on polyribosomes and cell-free protein synthesis in yeast

The treatment of yeast with thiopyronine (TP) caused a degradation of polyribosomes, even if the cells were not illuminated. In contrast, no differences in the polyribosome profiles of illuminated and unilluminated cells could be seen. Likewise, in in vitro experiments, there was no degradation of polyribosomes caused by dark effect or photodynamic action. Cell-free protein synthesis was inhibited up to 75 per cent by the photodynamic effect when the complete system was treated, but only up to 40 per cent when the polyribosomes or enzyme fraction were treated. Since the enzyme fraction contained aminoacyltRNA-synthetases and tRNA, it was necessary to investigate separately the effect of TP on the enzyme and the tTNA. It was shown that the aminoacyl-tRNA-synthetase and not tRNA was effected by the photodynamic action in its biological activity.