We have earlier reported two 26-residue antibacterial peptides made up from different segments ol'cecropin A (CA) and melittin (M). We now report a substantial reduction in size at the C-terminal section of the highly active hybrid CA(1–8)M(1–18), leading to a series of 20-, 18- and 15-residue analogs with antibiotic properties similar to the larger molecule. In particular, the 15-residue hybrids CA(1–7)M(2–9), CA(1–7)M(4–11) and CA(1–7)M(5–12) are the shortest cecropin-based peptide antibiotics described so far, with antibacterial activity and spectra similar or better than cecropin A and a 60% reduction in size. Their reduced size and highly α-helical structure require an alternative mechanism for their interaction with bacterial membranes.
