Specific hybridization of tyrosine transfer ribonucleic acids with DNA from a transducing bacteriophage φ80 carrying the amber suppressor gene suIII

Abstract

Transducing phages of φ80 have been isolated which carry the su III gene. We have used the technique of DNA-RNA hybridization to test the hypothesis that a tRNA Tyr molecule is the direct product of this gene. The following results strongly support this hypothesis: 1. (1) Upon infection of Escherichia coli by φ80 d su III , there is a tenfold increase in the fraction of the tRNA which will hybridize with φ80 d su III DNA. This is to be compared with a similar increase in the fraction of tRNA which will accept tyrosine following infection. 2. (2) Saturation experiments show that there is a single nucleotide sequence (a gene) which will hybridize with tRNA. 3. (3) As tRNA is purified for tyrosine-accepting activity, there is an increase in the fraction of the tRNA which will hybridize with φ80 d su III DNA. This has been shown both in saturation and in competition experiments. Our view of suppression dictates that there be at least two genes specifying tyrosine tRNA's in E. coli. One of the tRNA's, the major species, is not involved in suppression; the other, a minor species, recognizes the normal tyrosine codons in the su − cell, and UAG, a chain-terminating codon in the su + III cell. The present evidence shows that these two tRNA molecules must be very similar, as they both hybridize efficiently with φ80 d su III DNA.