Bac7(1-35) is a proline-rich AMP belonging to the cathelicidin family, can reach high concentrations (up to 340 μM) inside the E. coli cytoplasm. The peptide specifically and completely inhibits in vitro translation in the micromolar concentration range. Bac7(1–35) is a fully active fragment of Bac7, which translocates into susceptible bacteria by using a specific transporter, where it then interferes with ribosomes. Bac7(1–35), after crossing the membrane without lysis, acts by targeting ribosomes. Bac7(1–35) CD spectrum in phosphate buffer recalls that of the polyproline II conformation, which is not surprising considering the high percentage of proline residues in its primary structure.