N-Terminal analogs of cecropin A: synthesis, antibacterial activity, and conformational properties

Abstract
Six analogs of the 37-residue antibacterial peptide cecropin A were synthesized by the solid-phase method: cecropin A-(2-37), [Glu2]cecropin A [Pro4]cecropin A, [Glu6]cecropin A [Leu6] cecropin A, and [Pro8]cecropin A. Their antibacterial activities against 4 test organisms were determined and related to conformational changes observed in their CD spectra, and were discussed on the basis of a previously proposed amphipathic .alpha.-helix model. An aromatic residue in position 2 was shown to be important for activity against all tested bacteria. The highly .alpha.-helical 1-11 region of cecropin A did not appear to play a significant role in its activity against Escherichia coli, but was clearly involved in its interaction against Pseudomonas aeruginosa, Bacillus megaterium, and Micrococcus luteus.