Expression profiles of the opp-operon encoding an oligopeptide ABC-transport system. The bar-plots at the top of the figure display transcript levels of the indicated strains as compared with strain KF147. The deletion of a thymidine residue 64 bases upstream of the GTG-start codon of oppD in strains NZ5521 and NZ5522 is likely to explain the higher expression levels in these strains. In the same two strains, the deletion of an adenine residue (blue) in the upstream region of the truncated oppC gene generates an (alternative) start codon (purple), which is located 78 bases upstream of the native oppC start codon (green) and is preceded by a typical lactococcal ribosome binding site (red) that appears to be absent upstream of the native start codon. (*) Microarray probes designed to detect oppC are not 100% matching to the sequence of strain IL594—the actual expression level of oppC in strain IL594 might therefore be higher than indicated.
