| Abstract: | Yeast tRNAPhe was photoreacted with [3H]8-methoxypsoralen and the product was digested with ribonuclease T1, ribonuclease A or a combination of the two or cleaved with sodium borohydride/aniline. The oligonucleotides from these digestions were analyzed by polyacrylamide gel electrophoresis or high-pressure liquid chromatography and the psoralen-containing fragments were identified. The results indicate that one major and two minor photoreaction sites for 8-methoxypsoralen exist in yeast tRNAPhe. The major site (containing about 55% of the label) was determined as U50 in the T psi arm of the tRNA molecule while the minor sites were assigned to U59 (30% of the label) and C70 (15%) respectively. Our results suggest that psoralens may be used as photoprobes for studying conformational changes in tRNA molecules. |
