carbocyanines and pleurocidin

Pleurocidin, a 25-mer antimicrobial peptide, has been known to exhibit potent antibacterial activity. To investigate the functional roles in N- and C-terminal regions of pleurocidin on the antibacterial activity, we designed four truncated analogs. The antibacterial susceptibility testing showed that pleurocidin and its analogs exerted antibacterial effect against various bacterial strains and further possessed specific activity patterns corresponding with their hydrophobic scale [pleurocidin > Anal 3 (1-22) > Anal 1 (4-25) > Anal 4 (1-19) > Anal 2 (7-25)]. Fluorescence experiments using 1,6-diphenyl-1,3,5-hexatriene (DPH) and 3,3'-dipropylthiadicarbocyanine iodide [diSC3(5)] indicated that the differences in antibacterial activity of the peptides were caused by its membrane-active mechanisms including membrane disruption and depolarization. Blue shift in tryptophan fluorescence demonstrated that the decrease in net hydrophobicity attenuates the binding affinity of pleurocidin to interact with plasma membrane. Therefore, the present study suggests that hydrophobicity in the N- and C-terminal regions of pleurocidin plays a key role in its antibacterial activity.

Topics: Amino Acid Sequence; Anti-Bacterial Agents; Antimicrobial Cationic Peptides; Benzothiazoles; Carbocyanines; Cell Membrane; Diphenylhexatriene; Drug Resistance, Bacterial; Enterococcus faecium; Escherichia coli O157; Fish Proteins; Fluorescence; Hydrophobic and Hydrophilic Interactions; Microbial Sensitivity Tests; Molecular Sequence Data; Pseudomonas aeruginosa; Staphylococcus aureus; Tryptophan