Structure-function relationships in novel peptide dodecamerswith broad-spectrum bactericidal and endotoxin-neutralizing activities.
A series of designed peptide 33-mers (betapep peptides) areknown to be bactericidal [Mayo, Haseman, Ilyina and Gray (1998)Biochim. Biophys. Acta 1425, 81-92]. Here dodecapeptides (SC-1-SC-8), which 'walk through' the sequence ofbetapep-25, were investigated for their ability to kill Gram-negativeand -positive bacteria and to neutralize endotoxin. SC-4 (KLFKRHLKWKI I-NH(2); the -NH(2) at the right of each sequenceindicates amidation of the C-terminal carboxylate group) is the mosteffective, more so than betapep-25, at killing Gram-negative bacteriawith nanomolar LD(50) values. Against Gram-positive bacteria,SC-4 also shows good activity with submicromolar LD(50)values. Leakage studies indicate rapid bacterial membrane permeability,with t(1/2) valuesof 10-15 min. SC-4 in the micromolar range also effectivelyneutralizes endotoxin and is not haemolytic below 10(-4)M. For all SC peptides, CD and NMR data indicate the presence of both 3(10)- and alpha-helix. For SC-4, nuclear-Overhauser-effect-based computational modelling yields an amphipathic helix with K1, K4,R5, and K8 arrayed on the same face (K is lysine, R is arginine). Activity differences among SC peptides and single-site variants of SC-4allow some structure-function relationships to be deduced. Relative to other known bactericidal peptides in the linear peptide,helix-forming category, SC-4 is the most potent broad-spectrumantibacterial identified to date. The present study contributes to thedevelopment of agents involved in combating the ever-recurring problemof drug-resistant micro-organisms.
Mayo
K H
KH
Department of Biochemistry, Molecular Biology and Biophysics and The Biomedical Engineering Center, University of Minnesota Health Science Center, 6-155 Jackson Hall, 321 Church Street, Minneapolis, MN 55455, USA. mayox001@maroon.tc.umn.edu
Haseman
J
J
Young
H C
HC
Mayo
J W
JW
D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002942:Circular Dichroism; D004731:Endotoxins / Q000037:antagonists & inhibitors*; D006461:Hemolysis / Q000187:drug effects; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry*; D011550:Pseudomonas aeruginosa / Q000187:drug effects*; D013329:Structure-Activity Relationship
D000900:Anti-Bacterial Agents; D004731:Endotoxins; D010455:Peptides