FIG. 3.

Relative growth of strains with plasmids having UAA or NGG codons GGG, UGG, and CGG at early positions. Growth was measured in the presence of 75 μg/ml of erythromycin of the XAc strain carrying plasmids with the reporter gene 3A′ with the SD⁺ sequence and the E-peptide-encoding context in the beginning of the test gene, as described in the notes to Table 1. Growth of cultures in the presence of IPTG and 75 μg/ml of erythromycin is normalized relative to the growth in the presence of only IPTG. Black columns represent strains with plasmids with NGG codons in the early coding region, as indicated. Gray columns represent strains with plasmids bearing corresponding constructs with the NGG codon followed by a UAA stop codon. Open columns represent strains with plasmids that have UAA at positions +4, +5, +6, +7, or +8. The peptide sequences for these constructs are MIL, MILV, MSLKV, MSLKVL, or MSLKVLV, respectively. The peptide sequence encoded by NGG codons at position +3, +4, or +7, with or without a following UAA codon, is MIL, MILV or MSLKVL, respectively. The dotted line gives the background value for total inhibition of growth by erythromycin. Five independent experiments were performed, and values are expressed as the mean ± standard error.