Translocation of protegrin I through phospholipid membranes: role of peptide folding

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Abstract

The protegrin PG-1, belonging to the family of β-stranded antimicrobial peptides, exerts its activity by forming pores in the target biological membranes. Linear analogues derived from PG-1 do not form pores in the phospholipid membranes and have been used successfully to deliver therapeutic compounds into eucaryotic cells. In this paper, the translocation of PG-1 and of a linear analogue through artificial phospholipid membranes was investigated, leading to a possible mechanism for the activity of these peptidic vectors. We report here that [12W]PG-1, a fluorescent analogue of PG-1, is able to translocate through lipid bilayers and we demonstrate that this property depends on its secondary structure. Our results agree with the recent mechanism proposed for the translocation and permeabilisation activities of several helical and β-stranded peptides. In addition, our data corroborate recent work suggesting that certain protegrin-derived vectors enter into endothelial cells by adsorptive-mediated endocytosis.

Keywords

Peptide–lipid interaction
Protegrin
Translocation
Fluorescence
Peptidic vector

Abbreviations

CD, circular dichroism
DMF, N,N-dimethylformamide
DNS-PE, N-[5-(dimethylamino)-naphthyl]-1-sulfonyl]dipalmitoyl-l-α-phosphatidylethanolamine
LUVs, large unilamellar vesicles
MALDI-TOF MS, matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry
MLVs, multilamellar vesicles
NBD-PE, N-[7-nitrobenz-2-oxo-1,3-diazol-4-yl]dipalmitoyl]-l-α-phosphatidylethanolamine
POPC, 1-palmitoyl-2-oleyl-sn-glycero-3-phosphocholine
POPG, 1-palmitoyl-2-oleyl-sn-glycero-3-phosphoglycerol
P/L, peptide-to-lipid molar ratio
RET, resonance energy transfer
SUVs, small unilamellar vesicles
TMR, 5-(and-6)-carboxytetramethylrhodamine
TFE, 2,2,2-trifluoroethanol

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