Figure 3.

Repression of tisB translation by IstR-1. Translation of tisB mRNA is dependent on both a processing event and binding of the ribosome (purple) to a standby site (pink) as the real toxin ribosome binding site (yellow) is sequestered in a secondary structure. First, the full-length tisB mRNA (blue) must be processed at its 5' end in order for IstR-1 (red) or the ribosome to bind. Following processing, the standby site (pink) is accessible to the ribosome and the antitoxin (red; IstR-1). Binding by the antitoxin will block binding of the ribosome to the standby site. In the absence of the antitoxin, the ribosome can bind to the standby site and then onto the true ribosome binding site (yellow).