SOME PROPERTIES OF TRANSFER RIBONUCLEIC ACIDS FROM 5-FLUOROURACIL-TREATED ESCHERICHIA COLI

The composition and some of the functions of transfer ribonucleic acid from 5-fluorouracil-treated Escherichia coli have been examined. The analog can replace as much as 70% of the uracil in transfer ribonucleic acid. This substitution has little effect on the proportions of the other major nucleotide components: the purine to pyrimidine ratio remains unchanged. Transfer ribonucleic acid from 5-fluorouracil-inhibited cells is, however, deficient in several minor base components. The pseudouridylic acid content decreases from 2.7 to 0.99 mole %; this decrease is proportional to the extent of analog incorporation. The level of ribothymidylate in this ribonucleic acid is also reduced. Despite these changes in nucleotide composition the capacity of 5-fluorouracil-containing transfer ribonucleic acid to accept amino acids remains essentially the same as that of normal transfer ribonucleic acid. The mixture of transfer ribonucleic acid isolated from cells exposed to the analog can be partially separated into normal and 5-fluorouracil-containing components by chromatography on columns of methylated albumin silicic acid, with resolution increasing as the pH of the eluting buffer is raised from 5.2 to 8.0. The 5S ribosomal ribonucleic acid of 5-fluorouraciltreated cells also contains the analog; 35% of the uracil is replaced by 5-fluorouracil. This ribonucleic acid remains associated with the ribosome and does not contaminate the transfer ribonucleic acid fraction. © 1969, American Chemical Society. All rights reserved.