Photodynamic action and bacterial protein synthesis

Summary Photodynamic treatment of bacterial cells with thiopyronin and psoralen inhibits protein synthesis. Transfer RNA isolated from thiopyronin- and psoralen-treated cells is inactive in cell-free protein synthesis. Both the sensitizers inactivate transfer RNA to about 60 to 70%. Ribosomes isolated from thiopyronin-sensitized cells lose 45% of their activity, whereas under the influence of psoralen only 20% inactivation is observed. The enzyme fraction is not damaged in psoralen-treated bacteria, but thiopyronin inactivates this fraction as well. In vivo experiments indicate that psoralen does not react with the protein components of the cell. The mechanism of these inactivations is discussed.