Spermine-Conjugated Short Proline-Rich Lipopeptides as Broad-Spectrum Intracellular Targeting Antibacterial Agents

Toward the design of new proline-rich peptidomimetics, a short peptide segment, present in several proline-richantimicrobial peptides (AMPs), was selected. Fatty acids of varyinglengths and spermine were conjugated at the N- and C-terminals ofthe peptide, respectively. Spermine-conjugated lipopeptides, C10-PR-Spn and C12-PR-Spn, exhibited minimum inhibitory concen-trations within 1.5-6.2 mu M against the tested pathogens includingresistant bacteria and insignificant hemolytic activity againsthuman red blood cells up to 100 mu M concentrations anddemonstrated resistance against trypsin digestion. C10-PR-Spnand C12-PR-Spn showed synergistic antimicrobial activity againstmultidrug-resistant methicillin-resistantStaphylococcus aureuswithseveral tested antibiotics. These lipopeptides did not permeabilizebacterial membrane-mimetic lipid vesicles or damage theEscherichia colimembrane like the nonmembrane-lytic AMP, buforin-II.The results suggested that C10-PR-Spn and C12-PR-Spn could interact with the 70S ribosome ofE. coliand inhibit its proteinsynthesis. C10-PR-Spn and C12-PR-Spn demonstrated superior clearance of bacteria from the spleen, liver, and kidneys of mice,infected withS. aureus ATCC 25923 compared to levofloxacin