FIG. 5.

Suppressors of a −1 frameshift mutation and of a nearby +1 mutation. S. enterica trpE91 has a deletion of G₄₀₀ in its anthranilate synthetase gene (blue), which if not compensated for leads to termination at a UGA codon (brown). A fast-growing (pseudo-wild) revertant on media without tryptophan had an insertion of a C at 18 nucleotides 5′ (blue). The secondary compensatory mutation was separated by transduction and designated trpE872. The anticodons of tRNA mutants which suppress trpE872 are in green. One derivative of tRNA_mnm5UCC^Gly (tRNA₂^Gly) directly suppresses trpE91 by −1 frameshifting at G GGA, and others do so indirectly. An anticodon insertion mutant of tRNA_cmo5UAC^Val causes slipping +2 from GUG to GUG, and another mutant has C74 substituted. Mutants of L9 and RF2 facilitate +2 slippage by WT tRNA_cmo5UAC^Val from GUG to GUG.