FIG. 1.

Processing scheme of RP4 TrbC. The protein is shown as a box with its sequence in one-letter code inside. The 36-aa signal peptide and the 27-aa C-terminal cleaved peptide are shown as white boxes. The core sequence is shaded yellow with two predicted transmembranal helices (TMH) shown in blue. The 4-aa residues removed by TraF are inverted. Point mutations are annotated below or above the original sequence. Letters below indicate point mutants that are still cyclized by TraF; letters above indicate point mutants that are not processed by TraF. LepB and TraF are the enzymes that cleave TrbC, where “?” is the as-yet-unidentified host-encoded protease.