ROLE OF MODIFICATIONS IN TYROSINE TRANSFER RNA - A MODIFIED BASE AFFECTING RIBOSOME BINDING

Infection of Escherichia coli with the defective transducing bacteriophage φ80 dsu+III leads to a rapid and selective synthesis of suppressor tyrosine transfer RNA. Three forms of this suppressor transfer RNA have been isolated by reverse-phase column chromatography. The three forms have the same primary nucleotide sequence, but differ in the extent to which a base adjacent to the anticodon is modified. The three forms do not differ with respect to the rate at which they can be charged with tyrosine, but they do differ markedly in their abilities to support protein synthesis in vitro. The form which does not support protein synthesis is shown to be defective in its ability to bind to ribosomes. We conclude that the modification of the base adjacent to the anticodon in tyrosine transfer RNA is essential for its efficient binding to ribosomes, but not for its efficient charging. © 1969.