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- Melittin and the 8–26 fragment. Differences in ionophoric pr...Melittin and the 8–26 fragment. Differences in ionophoric properties as measured by monolayer method
Biophysical Journal, Volume 45, Issue 6, 1 June 1984, Pages 1079-1083
V.S. Gevod and K.S. Birdi
AbstractMelittin is a major (approximately 50%) protein component of bee venom. This peptide is an amphiphilic protein, because, while the amino acid residues 1–20 are predominantly hydrophobic (with the exception of Lys-7), residues 21–26 are hydrophilic. The binding properties to vesicles and lipid bilayers of melittin have provided much useful information regarding biological (hemolytic) activity (Habermann, E., 1972, Science [Wash. DC], 177:314–322). Recent studies have convincingly established that the melittin monolayer (at air-water interface) model membrane system allows one to analyze the various forces present in such structures. We present comparative monolayer studies of melittin and the peptide fragment 8–26 regarding the channel formation for the selective anion (Cl-) penetration in monolayers, analogous to melittin (tetramer) channel function in lipid bilayer. The differences in surface pressure and surface potential of monolayers between native melittin and the 8–26 fragment suggest that these may be ascribed to Lys-7.
Abstract | PDF (365 kb) - Antimicrobial Peptide-Lipid Binding Interactions and Binding...Antimicrobial Peptide-Lipid Binding Interactions and Binding Selectivity
Biophysical Journal, Volume 92, Issue 10, 15 May 2007, Pages 3575-3586
Mitaben D. Lad, Fabrice Birembaut, Luke A. Clifton, Richard A. Frazier, John R.P. Webster and Rebecca J. Green
AbstractSurface pressure measurements, external reflection-Fourier transform infrared spectroscopy, and neutron reflectivity have been used to investigate the lipid-binding behavior of three antimicrobial peptides: melittin, magainin II, and cecropin P1. As expected, all three cationic peptides were shown to interact more strongly with the anionic lipid, 1,2 dihexadecanoyl--glycerol-3-(phosphor-rac-(1-glycerol)) (DPPG), compared to the zwitterionic lipid, 1,2 dihexadecanoyl--glycerol-3-phosphocholine (DPPC). All three peptides have been shown to penetrate DPPC lipid layers by surface pressure, and this was confirmed for the melittin-DPPC interaction by neutron reflectivity measurements. Adsorption of peptide was, however, minimal, with a maximum of 0.4mg m seen for melittin adsorption compared to 2.1mg m for adsorption to DPPG (from 0.7M solution). The mode of binding to DPPG was shown to depend on the distribution of basic residues within the peptide -helix, although in all cases adsorption below the lipid layer was shown to dominate over insertion within the layer. Melittin adsorption to DPPG altered the lipid layer structure observed through changes in the external reflection-Fourier transform infrared lipid spectra and neutron reflectivity. This lipid disruption was not observed for magainin or cecropin. In addition, melittin binding to both lipids was shown to be 50% greater than for either magainin or cecropin. Adsorption to the bare air-water interface was also investigated and surface activity followed the trend melittin>magainin>cecropin. External reflection-Fourier transform infrared amide spectra revealed that melittin adopted a helical structure only in the presence of lipid, whereas magainin and cecropin adopted helical structure also at an air-water interface. This behavior has been related to the different charge distributions on the peptide amino acid sequences.
Abstract | Full Text | PDF (349 kb) - Infrared reflection-absorption of melittin interaction with ...Infrared reflection-absorption of melittin interaction with phospholipid monolayers at the air/water interface
Biophysical Journal, Volume 70, Issue 1, 1 January 1996, Pages 539-546
C.R. Flach, F.G. Prendergast and R. Mendelsohn
AbstractThe interaction of melittin with monolayers of 1,2-dipalmitoylphosphatidylcholine and 1,2-dipalmitoylphosphatidylserine has been investigated with infrared external reflection-absorption spectroscopy. Improved instrumentation permits determination of acyl chain conformation and peptide secondary structure in situ at the air/water interface. The IR frequency of the 1,2-dipalmitoylphosphatidylcholine antisymmetric acyl chain CH2 stretching vibration decreases by 1.3 cm-1 upon melittin insertion, consistent with acyl chain ordering, whereas the same vibrational mode increases by 0.5 cm-1 upon peptide interaction with the 1,2-dipalmitoylphosphatidylserine monolayer, indicative of chain disordering. Thus the peptide interacts quite differently with zwitterionic compared with negatively charged monolayer surfaces. Melittin in the monolayer adopted a secondary structure with an amide l(l') frequency (1635 cm-1) dramatically different from the alpha-helical motif (amide l frequency 1656 cm-1 in a dry or H2O hydrated environment, amide l' frequency 1645 cm-1 in an H-->D exchanged alpha-helix) assumed in bilayer or multibilayer environments. This work represents the first direct in situ spectroscopic indication that peptide secondary structure in lipid monolayers may differ from that in bilayers.
Abstract | PDF (813 kb) - …more
Copyright © 1996 The Biophysical Society. All rights reserved.
Biophysical Journal, Volume 71, Issue 3, 1422-1427, 1 September 1996
doi:10.1016/S0006-3495(96)79343-8
Research Article
Preferential partitioning of melittin into the air/water interface: structural and thermodynamic implications
G. Wackerbauer, I. Weis and G. Schwarz
Department of Biophysical Chemistry, University of Basel, Switzerland.
Abstract
The membrane active agent melittin has been investigated with regard to the formation of a Langmuir monolayer and the accordingly induced surface activities. We show that in spite of its considerable solubility in an aqueous medium, this peptide nevertheless largely accumulates in the air/water interface unless the lateral pressure is raised beyond a certain threshold value depending on the pH in the subphase. The true surface concentrations have been determined by means of a recently developed novel method based on thermodynamic principles. It affords an access to the partitioning equilibrium between the surface and subphase domains, provided the latter surrounding is not excessively preferred. In the present case this approach was used to derive quantitative information on the pertinent interfacial structure and thermodynamics. In particular, the apparent molecular area and the Gibbs energy of mutual interaction in the monolayer could be evaluated as a function of the applied surface pressure. The data suggest the existence of two structural conversions in the course of an increasing lateral compression. The surface-associated peptide accordingly assumes three different states of successively reduced area requirements, supposedly owing to an orientational transition involving a straightening up of a helical conformation. This conclusion is corroborated by surface potential measurements reflecting corresponding changes of the effective dipole moment perpendicular to the surface.
