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Titolo:
INTERACTIONS BETWEEN HUMAN DEFENSINS AND LIPID BILAYERS - EVIDENCE FOR FORMATION OF MULTIMERIC PORES
Autore:
WIMLEY WC; SELSTED ME; WHITE SH;
Indirizzi:
UNIV CALIF IRVINE,DEPT PHYSIOL & BIOPHYS IRVINE CA 92717 UNIV CALIF IRVINE,DEPT PHYSIOL & BIOPHYS IRVINE CA 92717 UNIV CALIF IRVINE,DEPT PATHOL IRVINE CA 92717
Titolo Testata:
Protein science
fascicolo: 9, volume: 3, anno: 1994,
pagine: 1362 - 1373
SICI:
0961-8368(1994)3:9<1362:IBHDAL>2.0.ZU;2-E
Fonte:
ISI
Lingua:
ENG
Soggetto:
ION-PERMEABLE CHANNELS; ANTIMICROBIAL PEPTIDES; ANTIBACTERIAL PEPTIDES; NEUTROPHIL DEFENSIN; VESICLE CONTENTS; PANETH CELLS; HOST DEFENSE; PURIFICATION; MEMBRANE; FUSION;
Keywords:
ANTIMICROBIAL PEPTIDES; FLUORESCENCE QUENCHING ASSAYS; HUMAN DEFENSIN HNP-2; LARGE UNILAMELLAR VESICLES (LUV); PEPTIDE BILAYER INTERACTIONS; VESICLE FUSION; VESICLE PERMEABILIZATION;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
61
Recensione:
Indirizzi per estratti:
Citazione:
W.C. Wimley et al., "INTERACTIONS BETWEEN HUMAN DEFENSINS AND LIPID BILAYERS - EVIDENCE FOR FORMATION OF MULTIMERIC PORES", Protein science, 3(9), 1994, pp. 1362-1373

Abstract

Defensins comprise a family of broad-spectrum antimicrobial peptides that are stored in the cytoplasmic granules of mammalian neutrophils and Paneth cells of the small intestine. Neutrophil defensins are knownto permeabilize cell membranes of susceptible microorganisms, but themechanism of permeabilization is uncertain. We report here the results of an investigation of the mechanism by which HNP-2, one of 4 human neutrophil defensins, permeabilizes large unilamellar vesicles formed from the anionic lipid palmitoyloleoylphosphatidylglycerol (POPG). As observed by others, we find that HNP-2 (net charge = +3) cannot bind to vesicles formed from neutral lipids. The binding of HNP-2 to vesicles containing varying amounts of POPG and neutral (zwitterionic) palmitoyloleoylphosphatidylcholine (POPC) demonstrates that binding is initiated through electrostatic interactions. Because vesicle aggregation and fusion can confound studies of the interaction of HNP-2 with vesicles, those processes were explored systematically by varying the concentrations of vesicles and HNP-2, and the POPG:POPC ratio. Vesicles (300mu M POPG) readily aggregated at HNP-2 concentrations above 1 mu M, but no mixing of vesicle contents could be detected for concentrations as high as 2 mu M despite the fact that intervesicular lipid mixing could be demonstrated. This indicates that if fusion of vesicles occurs,it is hemi-fusion, in which only the outer monolayers mix at bilayer contact sites. Under conditions of limited aggregation and intervesicular lipid mixing, the fractional leakage of small solutes is a sigmoidal function of peptide concentration. For 300 mu M POPG vesicles, 50% of entrapped solute is released by 0.7 mu M HNP-2. We introduce a simple method for determining whether leakage from vesicles is graded or all-or-none. We show by means of this fluorescence ''requenching'' method that native HNP-2 induces vesicle leakage in an all-or-none manner,whereas reduced HNP-2 induces partial, or graded, leakage of vesicle contents. At HNP-2 concentrations that release 100% of small (similar to 400 Da) markers, a fluorescent dextran of 4,400 Da is partially retained in the vesicles, and a 18,900-Da dextran is mostly retained. These results suggest that HNP-2 can form pores that have a maximum diameter of approximately 25 Angstrom. A speculative multimeric model of the pore is presented based on these results and on the crystal structure of a human defensin.

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Documento generato il 06/12/20 alle ore 00:02:56