A ribosomal frameshifting error during translation of the argl mRNA of Escherichla coli

Using fusions between the Escherichia coli genes argI and lacZ, it has been demonstrated that ribosomal frameshifting occurs at a frequency of between 3% and 16% within the argl mRNA, soon after the initiation codon. The frameshift involves a phenylalanyl-tRNA shifting into the + 1 frame at the sequence UUU-U/C. The shift does not occur if the in-frame phenylalanine codon UUU is replaced by UUC. The level of frameshifting is higher in dense cultures and is not dependent on phenylalanine starvation. In the wild-type argI gene this frameshifting event would be an error, leading to a truncated, non-functional protein. Therefore, it is unlike the numerous examples of required frameshifting events that have been described in other genes.