Codon specificity of UGA suppressor tRNATrp from Escherichia coli.

Abstract
A synthetic polyribonucleotide, poly(U5,G), was used to study the codon specificity of wild-type and UGA suppressor tRNATrp from E. coli. Phe (UUU) incorporation directed by this synthetic messenger is reduced somewhat by omission from the incubation mixtures of Val (GUU), Leu (UUG) or Cys (UGU). Omission of Cys stimulates Trp incorporation, and this effect is much more pronounced with the UGA suppressor tRNATrp than with wild-type tRNA. The apparent replacement of Cys by Trp is specific, because the omission of Val or Leu slightly inhibits Trp incorporation. The UGA suppressor tRNATrp can probably translate codons of the form UGN (N is any ribonucleotide). The suppressor tRNATrp translates codons that properly match 2 out of the 3 anticodon nucleotides.