Structure and mechanism of action of an indolicidin peptide derivative with improved activity against gram-positive bacteria.
Indolicidin, an antimicrobial peptide with a unique amino acid sequence (ILPWKWPWWPWRR-NH(2)) is found in bovine neutrophils. A derivative of indolicidin, CP10A, has alanine residues substituted for proline residues and has improved activity against Gram-positive organisms. Transmission electron microscopy of Staphylococcus aureus and Staphylococcus epidermidis treated with CP10A showed mesosome-like structures in the cytoplasm. The peptide at 2-fold the minimal inhibitory concentration did not show significant killing of S. aureus ISP67 (a histidine, uridine, and thymidine auxotroph) but did show an early effect on histidine and uridine incorporation and, later, an effect on thymidine incorporation. Upon interaction with liposomes, detergents, and lipoteichoic acid, CP10A was shown by circular dichroism spectroscopy to undergo a change in secondary structure. Fluorescence spectroscopy indicated that the tryptophan residues were located at the hydrophobic/hydrophilic interface of liposomes and detergent micelles and were inaccessible to the aqueous quencher KI. The three-dimensional structure of CP10A in the lipid mimetic dodecylphosphocholine was determined using two-dimensional NMR methods and was characterized as a short, amphipathic helical structure, whereas indolicidin was previously shown to have an extended structure. These studies have introduced a cationic peptide with a unique structure and an ability to interact with membranes and to affect intracellular synthesis of proteins, RNA, and DNA.
Friedrich
C L
CL
Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada.
Rozek
A
A
Patrzykat
A
A
Hancock
R E
RE
D023181:Antimicrobial Cationic Peptides / Q000737:chemistry* / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects; D002942:Circular Dichroism; D004269:DNA, Bacterial / Q000378:metabolism; D003902:Detergents / Q000378:metabolism; D006094:Gram-Positive Bacteria / Q000187:drug effects*; D008081:Liposomes / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008826:Microbial Sensitivity Tests; D008854:Microscopy, Electron; D008958:Models, Molecular; D012329:RNA, Bacterial / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D013211:Staphylococcus aureus / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D013212:Staphylococcus epidermidis / Q000187:drug effects / Q000648:ultrastructure
D023181:Antimicrobial Cationic Peptides; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D003902:Detergents; D008081:Liposomes; D012329:RNA, Bacterial; C432407:indolicidin derivative, CP10A