Membrane thinning caused by magainin 2

Ludtke, Steven J.; He, Ke; Huang, Huey W.

doi:10.1021/bi00051a026

Cited by 307 publications

(318 citation statements)

References 20 publications

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“…A membrane area increase, ∆A, causes a thinning of the chain region, -∆h, by the relation -∆h/h ) ∆A/A. Indeed, we have found that in all cases the bilayer thickness decreases linearly with increasing P/L (34,37,38,42,53) until P/L reaches a critical value, (P/L)*. Thus the slope of the membrane thickness versus P/L below (P/L)* (Figure 6) gives the value of A P ( Table 1).…”

Section: Experimental Parametersmentioning

confidence: 67%

Energetics of Pore Formation Induced by Membrane Active Peptides

2004

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Antimicrobial peptides are known to form pores in cell membranes. We study this process in model bilayers of various lipid compositions. We use two of the best-studied peptides, alamethicin and melittin, to represent peptides making two types of pores, that is, barrel-stave pores and toroidal pores. In both cases, the key control variable is the concentration of the bound peptides in the lipid bilayers (expressed in the peptide-lipid molar ratio, P/L). The method of oriented circular dichroism (OCD) was used to monitor the peptide orientation in bilayers as a function of P/L. The same samples were scanned by X-ray diffraction to measure the bilayer thickness. In all cases, the bilayer thickness decreases linearly with P/L and then levels off after P/L exceeds a lipid-dependent critical value, (P/L)*. OCD spectra showed that the helical peptides are oriented parallel to the bilayers as long as P/L < (P/L)*, but as P/L increases over (P/L)*, an increasing fraction of peptides changed orientation to become perpendicular to the bilayer. We analyzed the data by assuming an internal membrane tension associated with the membrane thinning. The free energy containing this tension term leads to a relation explaining the P/L-dependence observed in the OCD and X-ray diffraction measurements. We extracted the experimental parameters from this thermodynamic relation. We believe that they are the quantities that characterize the peptide-lipid interactions related to the mechanism of pore formation. We discuss the meaning of these parameters and compare their values for different lipids and for the two different types of pores. These experimental parameters are useful for further molecular analysis and are excellent targets for molecular dynamic simulation studies.Membrane active peptides, including antimicrobials and toxins, are known to induce transmembrane pores. The first peptide discovered to do so is alamethicin (1, 2). At first, alamethicin was thought to induce pores (which were detected by ion conduction) only by a transmembrane electric potential (see review in ref 3). However, numerous experiments (4-8) indicated that alamethicin could insert into bilayers in the absence of an external field (see review in ref 9). Although it was believed that alamethicin insertion would create pores, a direct correlation with ion conduction was difficult to establish. Later, with the combination of oriented circular dichroism (10, 11) and neutron diffraction (12, 13), we showed the direct correlation between alamethicin insertion (without voltage) and transmembrane pores. Two other extensively studied peptides, bee venom toxin melittin (14) and frog peptide magainin (15), also exhibited similar behaviors. Pores were evidently formed by both melittin (16-18) and magainin (19,20) because they caused leakage of fluorescent dyes from lipid vesicles. In the last 15 years, a great variety of antimicrobial peptides have been shown to induce transmembrane pores in bacterial cells as well as in lipid vesicles (see reviews in refs 2...

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Section: Experimental Parametersmentioning

confidence: 67%

Energetics of Pore Formation Induced by Membrane Active Peptides

2004

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“…Skin permeability to fluorescein was significantly increased (Student's t-test, p<0.01), but permeability to the two larger molecules was not significantly affected by magainin (Student's t-test, p>0.05). This can be explained because magainin is believed to form Angstrom-scale pores across lipid bilayers that are known to be large enough for transport only of small molecules [9,10].…”

Section: Resultsmentioning

confidence: 99%

Optimization of transdermal delivery using magainin pore-forming peptide

Kim

Ludovice

Prausnitz

2008

Journal of Physics and Chemistry of Solids

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The skin's outer layer of stratum corneum, which is a thin tissue containing multilamellar lipid bilayers, is the main barrier to drug delivery to the skin. To increase skin permeability, our previous work has shown large enhancement of transdermal permeation using a pore-forming peptide, magainin, which was formulated with N-lauroyl sarcosine (NLS) in 50% ethanol-in-PBS. Mechanistic analysis suggested that magainin and NLS can increase skin permeability by disrupting stratum corneum lipid structure. In this study, our goal was to improve conditions that increase skin permeability by magainin by further optimizing the pretreatment time and concentration of magainin exposure. We found that skin permeability increased with increasing pretreatment time. Skin permeability also increased with increasing magainin concentration up to 1 mM, but was reduced at a magainin concentration of 2 mM. Enhancement of skin permeability to fluorescein (323 Da) up to 35-fold was observed. In contrast, this formulation did not enhance skin permeability to larger molecules, such as calcein (623 Da) and dextran (3,000 Da).

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“…Then Fourier Shell Correlation (FSC) was calculated between both maps applying the 0.5 FSC threshold. Second, we performed the even-odd test in EMAN 37,39 in which two maps were obtained following the last cycle of refinement from the even and odd numbered particles and compared by FSC.…”

Section: Three-dimensional Reconstruction and Visualization Of Mapsmentioning

confidence: 99%

Structure of the Blm10–20 S Proteasome Complex by Cryo-electron Microscopy. Insights into the Mechanism of Activation of Mature Yeast Proteasomes

Iwanczyk

Sadre-Bazzaz

Ferrell

et al. 2006

Journal of Molecular Biology

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The 20S proteasome is regulated at multiple levels including association with endogenous activators. Two activators have been described for the yeast 20S proteasome: the 19S regulatory particle and the Blm10 protein. The sequence of Blm10 is 20% identical to the mammalian PA200 protein. Recent studies have shown that the sequences of Blm10 and PA200 each contain multiple HEAT-repeats and that each binds to the ends of mature proteasomes, suggesting a common structural and biochemical function. In order to advance structural studies, we have developed an efficient purification method that produces high yields of stoichiometric Blm10-mature yeast 20S proteasome complexes and we constructed a three-dimensional (3D) model of the Blm10-20S complex from cryo-electron microscopy images. This reconstruction shows that Blm10 binds in a defined orientation to both ends of the 20S particle and contacts all the proteasome α subunits. Blm10 displays the solenoid folding predicted by the presence of multiple HEAT-like repeats and the axial gates on the α rings of the proteasome appear to be open in the complex. We also performed a genetic analysis in an effort to identify the physiological role of Blm10. These experiments, however, did not reveal a robust phenotype upon gene deletion, overexpression, or in a screen for synthetic effects. This leaves the physiological role of Blm10 unresolved, but challenges earlier findings of a role in DNA repair.

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Membrane thinning caused by magainin 2

Cited by 307 publications

References 20 publications

Energetics of Pore Formation Induced by Membrane Active Peptides

Energetics of Pore Formation Induced by Membrane Active Peptides

Optimization of transdermal delivery using magainin pore-forming peptide

Structure of the Blm10–20 S Proteasome Complex by Cryo-electron Microscopy. Insights into the Mechanism of Activation of Mature Yeast Proteasomes

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