The bacterial pheL gene encodes the leader peptide for the
phenylalanine biosynthetic operon. Translation of pheL mRNA controls transcription attenuation and, consequently, expression of the downstream pheA gene. Fifty-three unique pheL genes have been identified in sequenced genomes of the gamma subdivision. There are two groups of pheL genes, both of which are short and contain a run(s) of
phenylalanine codons at an inteRNAl position. One group is somewhat diverse and features different termination and 5-flanking codons. The other group, mostly restricted to Enterobacteria and including
Escherichia coli pheL, has a conserved nucleotide sequence that ends with UUC_CCC_UGA. When these three codons in E. coli pheL mRNA are in the ribosomal E-, P- and A-sites, there is an unusually high level, 15%, of +1 ribosomal frameshifting due to features of the nascent peptide sequence that include the penultimate
phenylalanine. This level increases to 60% with a natural, heterologous, nas... ...