ISSN:
1435-1536
Keywords:
Tachyplesin I
;
lipid membrane
;
permeability
;
aggregation
;
fusion
;
micellization
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract Tachyplesin I, a broad-spectrum antimicrobial peptide fromTachypleus tridentatus has a basic (+7), amphiphilic, and cyclic β-sheet structure. We reported (Matsuzaki K. et al. (1991) Biochim. Biophys. Acta 1070:259–264) that 1) the action mechanism of tachyplesin I may be the permeabilization of bacterial membranes, 2) the peptide specifically permeabilizes acidic phospholipid bilayers, and 3) its Trp2 residue is located in the hydrophobic region near the surface of the bilayers. In this paper, we found that tachyplesin I dose-dependently induces not only the permeabilization but also aggregation/fusion and micellization of the phosphatidylglycerol large unilamellar vesicles (100 nm in diameter) either in the gel (L-α-dipalmitoylphosphatidyl-DL-glycerol (DPPG)) or liquid-crystalline (egg yolk L-α-phosphatidyl-DL-glycerol (egg PG)) phase, as revealed by light scattering and electron micrograph techniques. The solid DPPG vesicles were more susceptible to the peptide. At peptide to lipid molar ratios (P/L) of 1/500 to 1/200, interpeptide interactions formed a pore through which calcein, a fluorescent dye, can leak out of the vesicles. The pore lifetime was longer in the DPPG vesicles. Further addition of the peptide caused aggregation and/or fusion of the vesicles. At a charge-neutralizingP/L ratio of 1/7, the enlarged vesicles disintegrated into small spherical particles (10–20 nm in diameter). The mechanism for these morphological changes will be discussed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00652773
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