201
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Dalla Serra M, Cirioni O, Vitale RM, Renzone G, Coraiola M, Giacometti A, Potrich C, Baroni E, Guella G, Sanseverino M, De Luca S, Scalise G, Amodeo P, Scaloni A. Structural features of distinctin affecting peptide biological and biochemical properties. Biochemistry 2008; 47:7888-99. [PMID: 18597491 DOI: 10.1021/bi800616k] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The antimicrobial peptide distinctin consists of two peptide chains linked by a disulfide bridge; it presents a peculiar fold in water resulting from noncovalent dimerization of two heterodimeric molecules. To investigate the contribution of each peptide chain and the S-S bond to distinctin biochemical properties, different monomeric and homodimeric peptide analogues were synthesized and comparatively evaluated with respect to the native molecule. Our experiments demonstrate that the simultaneous occurrence of both peptide chains and the disulfide bond is essential for the formation of the quaternary structure of distinctin in aqueous media, able to resist protease action. In contrast, distinctin and monomeric and homodimeric analogues exhibited comparable antimicrobial activities, suggesting only a partial contribution of the S-S bond to peptide killing effectiveness. Relative bactericidal properties paralleled liposome permeabilization results, definitively demonstrating that microbial membranes are the main target of distinctin activity. Various biophysical experiments performed in membrane-mimicking media, before and after peptide addition, provided information about peptide secondary structure, lipid bilayer organization, and lipid-peptide orientation with respect to membrane surface. These data were instrumental in the generation of putative models of peptide-lipid supramolecular pore complexes.
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Affiliation(s)
- Mauro Dalla Serra
- Bruno Kessler Foundation, Institute of Biophysics, National Research Council, 38100 Povo, Trento, Italy
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202
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Hickel A, Danner-Pongratz S, Amenitsch H, Degovics G, Rappolt M, Lohner K, Pabst G. Influence of antimicrobial peptides on the formation of nonlamellar lipid mesophases. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2008; 1778:2325-33. [PMID: 18582435 DOI: 10.1016/j.bbamem.2008.05.014] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2008] [Revised: 05/30/2008] [Accepted: 05/30/2008] [Indexed: 10/22/2022]
Abstract
We have studied the influence of four antimicrobial peptides of different secondary and ternary structure--melittin (Mel), protegrin-1 (PG-1), peptidyl-glycylleucine-carboxyamide (PGLa), and gramicidin S (GS)--on the lamellar-to-nonlamellar transition of palmitoyloleoyl phosphatidylethanolamine (POPE) applying differential scanning calorimetry and small-angle X-ray diffraction. None of the peptides studied led to the formation of an inverted hexagonal phase observed for pure POPE at high temperatures. Instead either cubic or lamellar phases were stabilized to different degrees. GS was most effective in inducing a cubic phase, whereas Mel fully stabilized the lamellar phase. The behavior of POPE in the presence of PG-1 and PGLa was intermediate to GS and Mel. In addition to the known role of membrane elasticity we propose two mechanisms, which cause stabilization of the lamellar phase: electrostatic repulsion and lipid/peptide pore formation. Both mechanisms prevent transmembrane contact required to form either an inverted hexagonal phase or fusion pores, as precursors of the cubic phase.
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Affiliation(s)
- Andrea Hickel
- Institute of Biophysics and Nanosystems Research, Austrian Academy of Sciences, Schmiedlstrasse 6, A 8042 Graz, Austria
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203
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Qian S, Wang W, Yang L, Huang HW. Structure of the alamethicin pore reconstructed by x-ray diffraction analysis. Biophys J 2008; 94:3512-22. [PMID: 18199659 PMCID: PMC2292392 DOI: 10.1529/biophysj.107.126474] [Citation(s) in RCA: 118] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2007] [Accepted: 12/14/2007] [Indexed: 11/18/2022] Open
Abstract
We reconstructed the electron density profile of the alamethicin-induced transmembrane pore by x-ray diffraction. We prepared fully hydrated multiple bilayers of alamethicin-lipid mixtures in a condition where pores were present, as established previously by neutron in-plane scattering in correlation with oriented circular dichroism. At dehydrated conditions, the interbilayer distance shortened and the interactions between bilayers caused the membrane pores to become long-ranged correlated and form a periodically ordered lattice of rhombohedral symmetry. To resolve the phase problem of diffraction, we used a brominated lipid and performed multiwavelength anomalous diffraction at the bromine K edge. The result unambiguously shows that the alamethicin pore is of the barrel-stave type consisting of eight alamethicin helices. This pore structure corresponds to the stable pores detected by neutron in-plane scattering in fully hydrated fluid bilayers at high peptide/lipid ratios, which are the conditions at which alamethicin was tested for its antibacterial activity.
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Affiliation(s)
- Shuo Qian
- Department of Physics and Astronomy, Rice University, Houston, Texas 77251, USA
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204
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Carotenuto A, Malfi S, Saviello MR, Campiglia P, Gomez-Monterrey I, Mangoni ML, Gaddi LMH, Novellino E, Grieco P. A different molecular mechanism underlying antimicrobial and hemolytic actions of temporins A and L. J Med Chem 2008; 51:2354-62. [PMID: 18370376 DOI: 10.1021/jm701604t] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In this work, the naturally occurring antimicrobial peptides temporin A (TA) and L (TL) are studied by spectroscopic (CD and NMR) techniques and molecular dynamics simulation. We analyzed the interactions of TA and TL with sodium dodecyl sulfate (SDS) and dodecylphosphocholine (DPC) micelles, which mimic bacterial and mammalian membranes, respectively. In SDS, the peptides prefer a location at the micelle-water interface; in DPC, they prefer a location perpendicular to the micelle surface, with the N-terminus imbedded in the hydrophobic core. TL shows higher propensity, with respect to TA, in forming alpha-helical structures in both membrane mimetic systems and the highest propensity to penetrate the micelles. Hence, we have proposed a different molecular mechanism underlying the antimicrobial and hemolytic activities of the two peptides. We also designed new analogues of TA and TL and found interesting differences in their efficacy against microbial species and human erythrocytes.
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Affiliation(s)
- Alfonso Carotenuto
- Department of Pharmaceutical and Toxicological Chemistry, University of Naples "Federico II", I-80131 Naples, Italy
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205
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206
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Doherty T, Waring AJ, Hong M. Dynamic Structure of Disulfide-Removed Linear Analogs of Tachyplesin-I in the Lipid Bilayer from Solid-State NMR. Biochemistry 2007; 47:1105-16. [DOI: 10.1021/bi701390t] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Tim Doherty
- Department of Chemistry, Iowa State University, Ames, Iowa 50011, and Department of Medicine, University of California at Los Angeles, Los Angeles, California 90095
| | - Alan J. Waring
- Department of Chemistry, Iowa State University, Ames, Iowa 50011, and Department of Medicine, University of California at Los Angeles, Los Angeles, California 90095
| | - Mei Hong
- Department of Chemistry, Iowa State University, Ames, Iowa 50011, and Department of Medicine, University of California at Los Angeles, Los Angeles, California 90095
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207
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Microbicidal properties and cytocidal selectivity of rhesus macaque theta defensins. Antimicrob Agents Chemother 2007; 52:944-53. [PMID: 18160518 DOI: 10.1128/aac.01090-07] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Rhesus macaque theta-defensins (RTDs) are unique macrocyclic antimicrobial peptides. The three RTDs (RTD 1-3), isolated from macaque leukocytes, have broad-spectrum antimicrobial activities in vitro and share certain structural features with acyclic porcine protegrins, which are microbicidal peptides of the cathelicidin family. To understand the structural features that confer the respective cytocidal properties to theta-defensins and protegrins, we determined and compared the biological properties of RTD 1-3 and protegrin 1 (PG-1) in assays for antimicrobial activity, bacterial membrane permeabilization, and toxicity to human cells. RTD 1-3 and PG-1 had similar microbicidal potencies against Escherichia coli, Staphylococcus aureus, and Candida albicans in low-ionic-strength (10 mM) buffers at pH 7.4. The inclusion of physiologic sodium chloride partially inhibited the microbicidal activities of the RTDs, and the degree of inhibition depended on the buffer used in the assay. Similarly, the inclusion of 10% normal human serum partially antagonized the bactericidal activities of all four peptides. In contrast, the microbicidal activities of PG-1 and RTD 1-3 against E. coli were unaffected by physiologic concentrations of calcium chloride and magnesium chloride. Treatment of E. coli ML35 cells with RTD 1-3 or PG-1 rapidly rendered the bacteria permeable to omicron-nitrophenyl-beta-D-galactopyranoside, and this was accompanied by the rapid entry of the RTDs. Finally, although PG-1 was toxic to human fibroblasts and caused a marked lysis of erythrocytes, the RTDs were not cytotoxic or hemolytic. Thus, compared to PG-1, RTD 1-3 possess substantially greater cytocidal selectivity against microbes. Surprisingly, the low cytotoxicity of the RTDs did not depend on the peptides' cyclic conformation.
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208
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Gotsch F, Romero R, Kusanovic JP, Mazaki-Tovi S, Pineles BL, Erez O, Espinoza J, Hassan SS. The fetal inflammatory response syndrome. Clin Obstet Gynecol 2007; 50:652-83. [PMID: 17762416 DOI: 10.1097/grf.0b013e31811ebef6] [Citation(s) in RCA: 384] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The fetal inflammatory response syndrome (FIRS) is a condition characterized by systemic inflammation and an elevation of fetal plasma interleukin-6. This syndrome has been observed in fetuses with preterm labor with intact membranes, preterm prelabor rupture of the membranes, and also fetal viral infections such as cytomegalovirus. FIRS is a risk factor for short-term perinatal morbidity and mortality after adjustment for gestational age at delivery and also for the development of long-term sequelae such as bronchopulmonary dysplasia and brain injury. Multiorgan involvement in FIRS has been demonstrated in the hematopoietic system, thymus, adrenal glands, skin, kidneys, heart, lung, and brain. This article reviews the fetal systemic inflammatory response as a mechanism of disease. Potential interventions to control an exaggerated inflammatory response in utero are also described.
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Affiliation(s)
- Francesca Gotsch
- Perinatology Research Branch, Intramural Division, NICHD/NIH/DHHS, Hutzel Women's Hospital, Bethesda, Maryland, USA
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209
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Park SC, Kim MH, Hossain MA, Shin SY, Kim Y, Stella L, Wade JD, Park Y, Hahm KS. Amphipathic alpha-helical peptide, HP (2-20), and its analogues derived from Helicobacter pylori: pore formation mechanism in various lipid compositions. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1778:229-41. [PMID: 17961502 DOI: 10.1016/j.bbamem.2007.09.020] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 03/20/2007] [Revised: 09/22/2007] [Accepted: 09/25/2007] [Indexed: 01/25/2023]
Abstract
In a previous study, we determined that HP(2-20) (residues 2-20 of parental HP derived from the N-terminus of Helicobacter pylori Ribosomal Protein L1) and its analogue, HPA3, exhibit broad-spectrum antimicrobial activity. The primary objective of the present study was to gain insight into the relevant mechanisms of action using analogues of HP(2-20) together with model liposomes of various lipid compositions and electron microscopy. We determined that these analogues, HPA3 and HPA3NT3, exert potent antibacterial effects in low-salt buffer and antifungal activity against chitin-containing fungi, while having little or no hemolytic activity or cytotoxicity against mammalian cell lines. Our examination of the interaction of HP(2-20) and its analogues with liposomes showed that the peptides disturb both neutral and negatively-charged membranes, as demonstrated by the release of encapsulated fluorescent markers. The release of fluorescent markers induced by HP(2-20) and its analogues was inversely related to marker size. The pore created by HP(2-20) shows that the radius is approximately 1.8 nm, whereas HPA3, HPA3NT3, and melittin have apparent radii between 3.3 and 4.8 nm. Finally, as shown by electron microscopy, the liposomes and various microbial cells treated with HPA3 and HPA3NT3 showed oligomerization and blebbing similar to that seen with melittin, while HP(2-20) exhibited flabbiness. These results suggest that HP(2-20) may exert its antibiotic effects through a small pore (about 1.8 nm), whereas HPA3 and HPA3NT3 formed pores of a size consistent with those formed by melittin.
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Affiliation(s)
- Seong-Cheol Park
- Research Center for Proteineous Materials (RCPM), Chosun University, Gwangju, Korea
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210
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Yang L, Gordon VD, Mishra A, Som A, Purdy KR, Davis MA, Tew GN, Wong GCL. Synthetic antimicrobial oligomers induce a composition-dependent topological transition in membranes. J Am Chem Soc 2007; 129:12141-7. [PMID: 17880067 DOI: 10.1021/ja072310o] [Citation(s) in RCA: 115] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Antimicrobial peptides (AMPs) are cationic amphiphiles that comprise a key component of innate immunity. Synthetic analogues of AMPs, such as the family of phenylene ethynylene antimicrobial oligomers (AMOs), recently demonstrated broad-spectrum antimicrobial activity, but the underlying molecular mechanism is unknown. Homologues in this family can be inactive, specifically active against bacteria, or nonspecifically active against bacteria and eukaryotic cells. Using synchrotron small-angle X-ray scattering (SAXS), we show that observed antibacterial activity correlates with an AMO-induced topological transition of small unilamellar vesicles into an inverted hexagonal phase, in which hexagonal arrays of 3.4-nm water channels defined by lipid tubes are formed. Polarized and fluorescence microscopy show that AMO-treated giant unilamellar vesicles remain intact, instead of reconstructing into a bulk 3D phase, but are selectively permeable to encapsulated macromolecules that are smaller than 3.4 nm. Moreover, AMOs with different activity profiles require different minimum threshold concentrations of phosphoethanolamine (PE) lipids to reconstruct the membrane. Using ternary membrane vesicles composed of DOPG:DOPE:DOPC with a charge density fixed at typical bacterial values, we find that the inactive AMO cannot generate the inverted hexagonal phase even when DOPE completely replaces DOPC. The specifically active AMO requires a threshold ratio of DOPE:DOPC = 4:1, and the nonspecifically active AMO requires a drastically lower threshold ratio of DOPE:DOPC = 1.5:1. Since most gram-negative bacterial membranes have more PE lipids than do eukaryotic membranes, our results imply that there is a relationship between negative-curvature lipids such as PE and antimicrobial hydrophobicity that contributes to selective antimicrobial activity.
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Affiliation(s)
- Lihua Yang
- Department of Materials Science & Engineering, University of Illinois at Urbana-Champaign, Illinois 61801, USA
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211
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Fung HK, Floudas CA, Taylor MS, Zhang L, Morikis D. Toward full-sequence de novo protein design with flexible templates for human beta-defensin-2. Biophys J 2007; 94:584-99. [PMID: 17827237 PMCID: PMC2157230 DOI: 10.1529/biophysj.107.110627] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
In this article, we introduce and apply our de novo protein design framework, which observes true backbone flexibility, to the redesign of human beta-defensin-2, a 41-residue cationic antimicrobial peptide of the innate immune system. The flexible design templates are generated using molecular dynamics simulations with both Generalized Born implicit solvation and explicit water molecules. These backbone templates were employed in addition to the x-ray crystal structure for designing human beta-defensin-2. The computational efficiency of our framework was demonstrated with the full-sequence design of the peptide with flexible backbone templates, corresponding to the mutation of all positions except the native cysteines.
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Affiliation(s)
- Ho Ki Fung
- Department of Chemical Engineering, Princeton University, Princeton, New Jersey, USA
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212
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Lam KLH, Ishitsuka Y, Cheng Y, Chien K, Waring AJ, Lehrer RI, Lee KYC. Mechanism of supported membrane disruption by antimicrobial peptide protegrin-1. J Phys Chem B 2007; 110:21282-6. [PMID: 17048957 DOI: 10.1021/jp0630065] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
While pore formation has been suggested as an important step in the membrane disruption process induced by antimicrobial peptides, membrane pore formation has never been directly visualized. We report on the dynamics of membrane disruption by antimicrobial peptide protegrin-1 (PG-1) on dimyristoyl-sn-glycero-phosphocholine-supported bilayer patches obtained via atomic force microscopy. The action of PG-1 is found to be concentration-dependent. At low PG-1 concentrations (1 < [PG-1] < 4 microg/mL), the peptide destabilizes the edge of the membrane to form fingerlike structures. At higher concentrations, PG-1 induces the formation of a sievelike nanoporous structure in the membrane. The highest degree of disruption is attained at concentrations >or=20 microg/mL, at which PG-1 disrupts the entire membrane, transforming it into stripelike structures with a well-defined and uniform stripe width. This first direct visualization of these membrane structural transformations helps elucidate the PG-1-induced membrane disruption mechanism.
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Affiliation(s)
- Kin Lok H Lam
- Department of Physics, The Institute for Biophysical Dynamics, and The James Franck Institute, The University of Chicago, Illinois 60637, USA
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213
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Tang M, Waring AJ, Hong M. Phosphate-Mediated Arginine Insertion into Lipid Membranes and Pore Formation by a Cationic Membrane Peptide from Solid-State NMR. J Am Chem Soc 2007; 129:11438-46. [PMID: 17705480 DOI: 10.1021/ja072511s] [Citation(s) in RCA: 151] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The insertion of charged amino acid residues into the hydrophobic part of lipid bilayers is energetically unfavorable yet found in many cationic membrane peptides and protein domains. To understand the mechanism of this translocation, we measured the (13)C-(31)P distances for an Arg-rich beta-hairpin antimicrobial peptide, PG-1, in the lipid membrane using solid-state NMR. Four residues, including two Arg's, scattered through the peptide were chosen for the distance measurements. Surprisingly, all residues show short distances to the lipid (31)P: 4.0-6.5 A in anionic POPE/POPG membranes and 6.5-8.0 A in zwitterionic POPC membranes. The shortest distance of 4.0 A, found for a guanidinium Czeta at the beta-turn, suggests N-H...O-P hydrogen bond formation. Torsion angle measurements of the two Arg's quantitatively confirm that the peptide adopts a beta-hairpin conformation in the lipid bilayer, and gel-phase 1H spin diffusion from water to the peptide indicates that PG-1 remains transmembrane in the gel phase of the membrane. For this transmembrane beta-hairpin peptide to have short (13)C-(31)P distances for multiple residues in the molecule, some phosphate groups must be embedded in the hydrophobic part of the membrane, with the local (31)P plane parallel to the beta-strand. This provides direct evidence for toroidal pores, where some lipid molecules change their orientation to merge the two monolayers. We propose that the driving force for this toroidal pore formation is guanidinium-phosphate complexation, where the cationic Arg residues drag the anionic phosphate groups along as they insert into the hydrophobic part of the membrane. This phosphate-mediated translocation of guanidinium ions may underlie the activity of other Arg-rich antimocrobial peptides and may be common among cationic membrane proteins.
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Affiliation(s)
- Ming Tang
- Department of Chemistry, Iowa State University, Ames, Iowa 50011, USA
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214
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Kandasamy SK, Larson RG. Binding modes of protegrin-1, a beta-strand antimicrobial peptide, in lipid bilayers. MOLECULAR SIMULATION 2007. [DOI: 10.1080/08927020701313737] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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215
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Fázio MA, Jouvensal L, Vovelle F, Bulet P, Miranda MTM, Daffre S, Miranda A. Biological and structural characterization of new linear gomesin analogues with improved therapeutic indices. Biopolymers 2007; 88:386-400. [PMID: 17183513 DOI: 10.1002/bip.20660] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Gomesin (Gm) is a potent antimicrobial peptide isolated from the spider Acanthoscurria gomesiana. The two disulfide bridges Cys(2,15) and Cys(6,11) facilitate the folding of the molecule in a beta-hairpin structure, conferring on the peptide a high stability in human plasma. We report herein biological and structural features of new linear Gm analogues, obtained by combining the removal of both disulfide bridges and the incorporation of a D- or L-proline. Regarding their biological properties, two analogues, namely, [D-Thr(2,6,11,15), Pro(9)]-D-Gm and [Thr(2,6,11,15), D-Pro(9)]-Gm, are as potent as Gm against Candida albicans and only fourfold less against Staphylococcus aureus and Escherichia coli. In addition, at 100 microM they are approximately threefold less hemolytic than Gm. The best therapeutic indices were found for [D-Thr(2,6,11,15), Pro(9)]-D-Gm and for [(Des-pGlu(1), -Thr(2), -Arg(3)), Thr(6,11,15), D-Pro(9)]-Gm with a 32-fold increase of their activity against bacteria, and from 128- to 512-fold against yeast when compared with Gm. Regarding the stability, [D-Thr(2,6,11,15), Pro(9)]-D-Gm appeared to be the most resistant in human serum, along with [D-Thr(2,6,11,15), Pro(8)]-D-Gm and [Thr(2,6,11,15), D-Arg(4,16), D-Pro(9)]-Gm. When evaluating their conformation by CD spectroscopy in sodium dodecyl sulfate (SDS), most linear analogues display beta-conformation characteristics. Moreover, considering its high therapeutic index and stability in serum, [D-Thr(2,6,11,15), Pro(9)]-D-Gm was further analyzed by NMR spectroscopy. (1)H NMR experiments in SDS micelles demonstrated that [D-Thr(2,6,11,15), Pro(9)]-D-Gm presents a conformation very similar to that of Gm. In our search for Gm analogues with enhanced potential for drug development, we demonstrated that designing cysteine-free analogues can improve the therapeutic index of Gm derivatives.
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Affiliation(s)
- Marcos A Fázio
- Department of Biophysics, UNIFESP, 04044-020 São Paulo, SP, Brazil
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216
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Calabretta MK, Kumar A, McDermott AM, Cai C. Antibacterial activities of poly(amidoamine) dendrimers terminated with amino and poly(ethylene glycol) groups. Biomacromolecules 2007; 8:1807-11. [PMID: 17511499 PMCID: PMC2430505 DOI: 10.1021/bm0701088] [Citation(s) in RCA: 163] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Poly(amidoamine) (PAMAM) dendrimer derivatives have been investigated for their biological applications, especially for delivery of drugs, including antimicrobial drugs to eukaryotic cells, but their effects on bacterial cells are largely unexplored. Herein we report that amino-terminated PAMAM dendrimers are highly toxic to the common Gram-negative pathogen Pseudomonas aeruginosa. The concentration that kills 50% of the bacteria (EC50) was in the range of approximately 0.9-1.5 microg/mL for the generation 5, amino-terminated dendrimers with or without partial (43%) coating of poly(ethylene glycol) (PEG). These EC50 values were lower than that ( approximately 1.9-2.8 microg/mL) for LL-37, a potent antimicrobial peptide expressed in a variety of epithelia. On the contrary, the dendrimers were far less toxic (EC50 > 21 microg/mL) to the Gram-positive pathogen Staphylococcus aureus than LL-37 (EC50 = approximately 1.9 microg/mL). In agreement with the previous studies on other cell types, the dendrimers were not cytotoxic to human corneal epithelial cells at the concentrations that were toxic to P. aeruginosa. Our findings indicate that amino-terminated PAMAM dendrimers and their partially PEG-coated derivatives possess attractive antimicrobial properties, particularly against Gram-negative bacteria, thus expanding the potential biological application of the dendrimers.
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Affiliation(s)
| | - Amit Kumar
- Department of Chemistry, University of Houston, Houston, Texas 77204
| | | | - Chengzhi Cai
- Department of Chemistry, University of Houston, Houston, Texas 77204
- Author to whom correspondence should be addressed. E-mail: . Phone: (713)743-2710. Fax: (713)743-2709
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217
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Shental-Bechor D, Haliloglu T, Ben-Tal N. Interactions of cationic-hydrophobic peptides with lipid bilayers: a Monte Carlo simulation method. Biophys J 2007; 93:1858-71. [PMID: 17496025 PMCID: PMC1959530 DOI: 10.1529/biophysj.106.103812] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We present a computational model of the interaction between hydrophobic cations, such as the antimicrobial peptide, Magainin2, and membranes that include anionic lipids. The peptide's amino acids were represented as two interaction sites: one corresponds to the backbone alpha-carbon and the other to the side chain. The membrane was represented as a hydrophobic profile, and its anionic nature was represented by a surface of smeared charges. Thus, the Coulombic interactions between the peptide and the membrane were calculated using the Gouy-Chapman theory that describes the electrostatic potential in the aqueous phase near the membrane. Peptide conformations and locations near the membrane, and changes in the membrane width, were sampled at random, using the Metropolis criterion, taking into account the underlying energetics. Simulations of the interactions of heptalysine and the hydrophobic-cationic peptide, Magainin2, with acidic membranes were used to calibrate the model. The calibrated model reproduced structural data and the membrane-association free energies that were measured also for other basic and hydrophobic-cationic peptides. Interestingly, amphipathic peptides, such as Magainin2, were found to adopt two main membrane-associated states. In the first, the peptide resided mostly outside the polar headgroups region. In the second, which was energetically more favorable, the peptide assumed an amphipathic-helix conformation, where its hydrophobic face was immersed in the hydrocarbon region of the membrane and the charged residues were in contact with the surface of smeared charges. This dual behavior provides a molecular interpretation of the available experimental data.
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Affiliation(s)
- Dalit Shental-Bechor
- Department of Biochemistry, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Israel
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218
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Higgs R, Lynn DJ, Cahalane S, Alaña I, Hewage CM, James T, Lloyd AT, O'Farrelly C. Modification of chicken avian β-defensin-8 at positively selected amino acid sites enhances specific antimicrobial activity. Immunogenetics 2007; 59:573-80. [PMID: 17483936 DOI: 10.1007/s00251-007-0219-5] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2007] [Accepted: 03/20/2007] [Indexed: 11/30/2022]
Abstract
Antimicrobial peptides (AMPs), essential components of innate immunity, are found in a range of phylogenetically diverse species and are thought to act by disrupting the membrane integrity of microbes. In this paper, we used evolutionary signatures to identify sites that are most relevant during the functional evolution of these molecules and introduced amino acid substitutions to improve activity. We first demonstrate that the anti-microbial activity of chicken avian beta-defensin-8, previously known as gallinacin-12, can be significantly increased against Escherichia coli, Listeria monocytogenes, Salmonella typhimurium, Salmonella typhimurium phoP- mutant and Streptococcus pyogenes through targeted amino acid substitutions, which confer increased peptide charge. However, by increasing the AMP charge through amino acid substitutions at sites predicted to be subject to positive selection, antimicrobial activity against Escherichia coli was further increased. In contrast, no further increase in activity was observed against the remaining pathogens. This result suggests that charge-increasing modifications confer increased broad-spectrum activity to an AMP, whilst positive selection at particular sites is involved in directing the antimicrobial response against specific pathogens. Thus, there is potential for the rational design of novel therapeutics based on specifically targeted and modified AMPs.
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Affiliation(s)
- Rowan Higgs
- Education and Research Centre, St. Vincent's University Hospital, Dublin 4, Ireland
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219
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Constantin D, Brotons G, Jarre A, Li C, Salditt T. Interaction of alamethicin pores in DMPC bilayers. Biophys J 2007; 92:3978-87. [PMID: 17369412 PMCID: PMC1868975 DOI: 10.1529/biophysj.106.101204] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We have investigated the x-ray scattering signal of highly aligned multilayers of the zwitterionic lipid 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine containing pores formed by the antimicrobial peptide alamethicin as a function of the peptide/lipid ratio. We are able to obtain information on the structure factor of the pore fluid, which then yields the interaction potential between pores in the plane of the bilayers. Aside from a hard core with a radius corresponding to the geometric radius of the pore, we find a repulsive lipid-mediated interaction with a range of approximately 30 A and a contact value of 2.4 k(B)T. This result is in qualitative agreement with recent theoretical models.
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220
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Olsen CA, Bonke G, Vedel L, Adsersen A, Witt M, Franzyk H, Jaroszewski JW. α-Peptide/β-Peptoid Chimeras. Org Lett 2007; 9:1549-52. [PMID: 17352488 DOI: 10.1021/ol070316c] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
[structure: see text] We describe the synthesis and characterization of the first generation of oligomers consisting of alternating repeats of alpha-amino acids and chiral N-alkyl-beta-alanine (beta-peptoid) residues. These chimeras are stable toward proteolysis, non-hemolytic, and possess antibacterial activity comparable to well-known antimicrobial agents. Moreover, the chimeras exhibit length-dependent, concentration-dependent, solvent-dependent, and ion-strength-dependent ellipticity, indicating the presence of a secondary structure in solution. Thus, alpha-peptide/beta-peptoid oligomers represent a promising novel peptidomimetic backbone construct for biologically active ligands.
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Affiliation(s)
- Christian A Olsen
- Department of Medicinal Chemistry, Faculty of Pharmaceutical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark.
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221
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Radzishevsky I, Krugliak M, Ginsburg H, Mor A. Antiplasmodial activity of lauryl-lysine oligomers. Antimicrob Agents Chemother 2007; 51:1753-9. [PMID: 17307975 PMCID: PMC1855553 DOI: 10.1128/aac.01288-06] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The ever evolving resistance of the most virulent malaria parasite, Plasmodium falciparum, to antimalarials necessitates the continuous development of new drugs. Our previous analysis of the antimalarial activities of the hemolytic antimicrobial peptides dermaseptins and their acylated derivatives implicated the importance of hydrophobicity and charge for drug action. Following these findings, an oligoacyllysine (OAK) tetramer designed to mimic the characteristics of dermaseptin was synthesized and assessed for its antimalarial activity in cultures of P. falciparum. The tetramer inhibited the growth of different plasmodial strains at low micromolar concentrations (mean 50% inhibitory concentration [IC(50)], 1.8 microM). A structure-activity relationship study involving eight derivatives unraveled smaller, more potent OAK analogs (IC(50)s, 0.08 to 0.14 microM). The most potent analogs were the most selective, with selectivity ratios of 3 orders of magnitude. Selectivity was strongly influenced by the self-assembly properties resulting from interactions between hydrophobic OAKs, as has been observed with conventional antimicrobial peptides. Further investigations performed with a representative OAK revealed that the ring and trophozoite stages of the parasite developmental cycle were equally sensitive to the compound. A shortcoming of the tested compound was the need for long incubation times in order for it to exert its full effect. Nevertheless, the encouraging results obtained in this study regarding the efficiency and selectivity of some compounds establish them as leads for further development.
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Affiliation(s)
- I Radzishevsky
- Department of Biotechnology & Food Engineering, Technion-Israel Institute of Technology, Haifa, Israel
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222
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Lamazière A, Burlina F, Wolf C, Chassaing G, Trugnan G, Ayala-Sanmartin J. Non-metabolic membrane tubulation and permeability induced by bioactive peptides. PLoS One 2007; 2:e201. [PMID: 17299584 PMCID: PMC1790702 DOI: 10.1371/journal.pone.0000201] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2006] [Accepted: 01/18/2007] [Indexed: 11/19/2022] Open
Abstract
Background Basic cell-penetrating peptides are potential vectors for therapeutic molecules and display antimicrobial activity. The peptide-membrane contact is the first step of the sequential processes leading to peptide internalization and cell activity. However, the molecular mechanisms involved in peptide-membrane interaction are not well understood and are frequently controversial. Herein, we compared the membrane activities of six basic peptides with different size, charge density and amphipaticity: Two cell-penetrating peptides (penetratin and R9), three amphipathic peptides and the neuromodulator substance P. Methodology/Principal Findings Experiments of X ray diffraction, video-microscopy of giant vesicles, fluorescence spectroscopy, turbidimetry and calcein leakage from large vesicles are reported. Permeability and toxicity experiments were performed on cultured cells. The peptides showed differences in bilayer thickness perturbations, vesicles aggregation and local bending properties which form lipidic tubular structures. These structures invade the vesicle lumen in the absence of exogenous energy. Conclusions/Significance We showed that the degree of membrane permeabilization with amphipathic peptides is dependent on both peptide size and hydrophobic nature of the residues. We propose a model for peptide-induced membrane perturbations that explains the differences in peptide membrane activities and suggests the existence of a facilitated “physical endocytosis,” which represents a new pathway for peptide cellular internalization.
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Affiliation(s)
- Antonin Lamazière
- Institut National de la Santé et de la Recherche Médicale (INSERM), UMR 538, CHU Saint Antoine, Paris, France
- Université Pierre et Marie Curie, CHU Saint Antoine, Paris, France
| | - Fabienne Burlina
- UMR Centre National de la Recherche Scientifique (CNRS) 7613, Université Pierre et Marie Curie, Paris, France
| | - Claude Wolf
- Institut National de la Santé et de la Recherche Médicale (INSERM), UMR 538, CHU Saint Antoine, Paris, France
- Université Pierre et Marie Curie, CHU Saint Antoine, Paris, France
| | - Gérard Chassaing
- UMR Centre National de la Recherche Scientifique (CNRS) 7613, Université Pierre et Marie Curie, Paris, France
| | - Germain Trugnan
- Institut National de la Santé et de la Recherche Médicale (INSERM), UMR 538, CHU Saint Antoine, Paris, France
- Université Pierre et Marie Curie, CHU Saint Antoine, Paris, France
| | - Jesus Ayala-Sanmartin
- Institut National de la Santé et de la Recherche Médicale (INSERM), UMR 538, CHU Saint Antoine, Paris, France
- Université Pierre et Marie Curie, CHU Saint Antoine, Paris, France
- * To whom correspondence should be addressed. E-mail:
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223
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Wang W, Yang L, Huang HW. Evidence of cholesterol accumulated in high curvature regions: implication to the curvature elastic energy for lipid mixtures. Biophys J 2007; 92:2819-30. [PMID: 17259270 PMCID: PMC1831681 DOI: 10.1529/biophysj.106.097923] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Recent experiments suggested that cholesterol and other lipid components of high negative spontaneous curvature facilitate membrane fusion. This is taken as evidence supporting the stalk-pore model of membrane fusion in which the lipid bilayers go through intermediate structures of high curvature. How do the high-curvature lipid components lower the free energy of the curved structure? Do the high-curvature lipid components modify the average spontaneous curvature of the relevant monolayer, thereby facilitate its bending, or do the lipid components redistribute in the curved structure so as to lower the free energy? This question is fundamental to the curvature elastic energy for lipid mixtures. Here we investigate the lipid distribution in a monolayer of a binary lipid mixture before and after bending, or more precisely in the lamellar, hexagonal, and distorted hexagonal phases. The lipid mixture is composed of 2:1 ratio of brominated di18:0PC and cholesterol. Using a newly developed procedure for the multiwavelength anomalous diffraction method, we are able to isolate the bromine distribution and reconstruct the electron density distribution of the lipid mixture in the three phases. We found that the lipid distribution is homogenous and uniform in the lamellar and hexagonal phases. But in the distorted hexagonal phase, the lipid monolayer has nonuniform curvature, and cholesterol almost entirely concentrates in the high curvature region. This finding demonstrates that the association energies between lipid molecules vary with the curvature of membrane. Thus, lipid components in a mixture may redistribute under conditions of nonuniform curvature, such as in the stalk structure. In such cases, the spontaneous curvature depends on the local lipid composition and the free energy minimum is determined by lipid distribution as well as curvature.
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Affiliation(s)
- Wangchen Wang
- Department of Physics & Astronomy, Rice University, Houston, Texas, USA
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224
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Pan YL, Cheng JTJ, Hale J, Pan J, Hancock REW, Straus SK. Characterization of the structure and membrane interaction of the antimicrobial peptides aurein 2.2 and 2.3 from Australian southern bell frogs. Biophys J 2007; 92:2854-64. [PMID: 17259271 PMCID: PMC1831713 DOI: 10.1529/biophysj.106.097238] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The structure and membrane interaction of the antimicrobial peptide aurein 2.2 (GLFDIVKKVVGALGSL-CONH(2)), aurein 2.3 (GLFDIVKKVVGAIGSL-CONH(2)), both from Litoria aurea, and a carboxy C-terminal analog of aurein 2.3 (GLFDIVKKVVGAIGSL-COOH) were studied to determine which features of this class of peptides are key to activity. Circular dichroism and solution-state NMR data indicate that all three peptides adopt an alpha-helical structure in the presence of trifluoroethanol or lipids such as 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and a 1:1 mixture of DMPC and 1,2-dimyristoyl-sn-glycero-3-[phospho-rac-(1-glycerol)] (DMPG). Oriented circular dichroism was used to determine the orientation of the peptides in lipid bilayers over a range of concentrations (peptide/lipid molar ratios (P/L) = 1:15-1:120) in DMPC and 1:1 DMPC/DMPG, in the liquid crystalline state. The results demonstrate that in DMPC all three peptides are surface adsorbed over a range of low peptide concentrations but insert into the bilayers at high peptide concentrations. This finding is corroborated by (31)P-solid-state NMR data of the three peptides in DMPC, which shows that at high peptide concentrations the peptides perturb the membrane. Oriented circular dichroism data of the aurein peptides in 1:1 DMPC/DMPG, on the other hand, show that the peptides with amidated C-termini readily insert into the membrane bilayers over the concentration range studied (P/L = 1:15-1:120), whereas the aurein 2.3 peptide with a carboxy C-terminus inserts at a threshold concentration of P/L* between 1:80 and 1:120. Overall, the data presented here suggest that all three peptides studied interact with phosphatidylcholine membranes in a manner which is similar to aurein 1.2 and citropin 1.1, as reported in the literature, with no correlation to the reported activity. On the other hand, both aurein 2.2 and aurein 2.3 behave similarly in phosphatidylcholine/phosphatidylglycerol (PC/PG) membranes, whereas aurein 2.3-COOH inserts less readily. As this does not correlate with reported activities, minimal inhibitory concentrations of the three peptides against Staphylococcus aureus (strain C622, ATCC 25923) and Staphylococcus epidermidis (strain C621--clinical isolate) were determined. The correlation between structure, membrane interaction, and activity are discussed in light of these results.
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Affiliation(s)
- Yeang-Ling Pan
- Department of Chemistry, University of British Columbia, Vancouver, British Columbia, V6T 1Z1, Canada
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225
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Soto E, Espinoza J, Nien JK, Kusanovic J, Erez O, Richani K, Santolaya-Forgas J, Romero R. Human beta-defensin-2: a natural antimicrobial peptide present in amniotic fluid participates in the host response to microbial invasion of the amniotic cavity. J Matern Fetal Neonatal Med 2007; 20:15-22. [PMID: 17437194 PMCID: PMC3516412 DOI: 10.1080/14767050601036212] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
OBJECTIVE Human beta-defensin-2 (HBD-2) is a potent antimicrobial peptide that is part of the innate immune response. The purpose of this study was to determine whether HBD-2 is present in amniotic fluid and if its concentration changes with microbial invasion of the amniotic cavity (MIAC) and labor. STUDY DESIGN Amniotic fluid was retrieved by amniocentesis from 318 patients in the following groups: (1) mid-trimester (n=75); (2) term not in labor (n=28) and in labor (n=51); (3) preterm labor and intact membranes without MIAC who delivered at term (n=36), who delivered preterm without MIAC (n=52), and preterm labor with MIAC who delivered preterm (n=25); and (4) preterm premature rupture of membranes (preterm PROM) with (n=25) and without MIAC (n=26). MIAC was defined as a positive amniotic fluid culture for microorganisms. Amniotic fluid HBD-2 concentrations were determined using a sensitive and specific ELISA. Non-parametric statistics were used for analysis. RESULTS (1) HBD-2 was detected in all amniotic fluid samples; (2) the concentration of HBD-2 did not change with gestational age from mid-trimester to term (p=0.8); (3) intra-amniotic infection was associated with a significant increase in amniotic fluid concentrations of HBD-2 in both women with preterm labor and intact membranes, and women with preterm PROM (p<0.05 for each comparison); (4) patients with preterm labor and a negative amniotic fluid culture who delivered preterm had a higher median amniotic fluid HBD-2 concentration than those with preterm labor who delivered at term (p=0.001); and (5) among patients with preterm labor without MIAC, those who had intra-amniotic inflammation (amniotic fluid white blood cell count>100 cells per mL) had a higher median amniotic fluid concentration of HBD-2 than those without this condition (p<0.002). CONCLUSION (1) Amniotic fluid contains HBD-2, a natural antimicrobial peptide, and this may account for some of the antimicrobial activity of amniotic fluid; (2) amniotic fluid HBD-2 concentrations are increased in women with MIAC, regardless of the membrane status (intact membranes or PROM); and (3) we propose that amniotic fluid HBD-2 is part of the innate immune system within the amniotic cavity.
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Affiliation(s)
- Eleazar Soto
- Perinatology Research Branch, NICHD, NIH, DHHS, Bethesda, Maryland and Detroit, Michigan
| | - Jimmy Espinoza
- Perinatology Research Branch, NICHD, NIH, DHHS, Bethesda, Maryland and Detroit, Michigan
- Wayne State University School of Medicine, Department of Obstetrics and Gynecology, Detroit, Michigan
| | - Jyh Kae Nien
- Perinatology Research Branch, NICHD, NIH, DHHS, Bethesda, Maryland and Detroit, Michigan
| | - Juan Kusanovic
- Perinatology Research Branch, NICHD, NIH, DHHS, Bethesda, Maryland and Detroit, Michigan
| | - Offer Erez
- Perinatology Research Branch, NICHD, NIH, DHHS, Bethesda, Maryland and Detroit, Michigan
| | - Karina Richani
- Perinatology Research Branch, NICHD, NIH, DHHS, Bethesda, Maryland and Detroit, Michigan
| | - Joaquin Santolaya-Forgas
- Perinatology Research Branch, NICHD, NIH, DHHS, Bethesda, Maryland and Detroit, Michigan
- Wayne State University School of Medicine, Department of Obstetrics and Gynecology, Detroit, Michigan
| | - Roberto Romero
- Perinatology Research Branch, NICHD, NIH, DHHS, Bethesda, Maryland and Detroit, Michigan
- Center for Molecular Medicine and Genetics, Wayne State University, Detroit, Michigan
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226
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Romero R, Espinoza J, Gonçalves LF, Kusanovic JP, Friel L, Hassan S. The role of inflammation and infection in preterm birth. Semin Reprod Med 2007; 25:21-39. [PMID: 17205421 PMCID: PMC8324073 DOI: 10.1055/s-2006-956773] [Citation(s) in RCA: 626] [Impact Index Per Article: 36.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Inflammation has been implicated in the mechanisms responsible for preterm and term parturition, as well as fetal injury. Out of all of the suspected causes of preterm labor and delivery, infection and/or inflammation is the only pathological process for which both a firm causal link with preterm birth has been established and a molecular pathophysiology defined. Inflammation has also been implicated in the mechanism of spontaneous parturition at term. Most cases of histopathological inflammation and histological chorioamnionitis, both in preterm and term labor, are sub-clinical in nature. The isolation of bacteria in the amniotic fluid, known as microbial invasion of the amniotic cavity, is a pathological finding; the frequency of which is dependent upon the clinical presentation and gestational age. This article reviews the role of inflammation in preterm and term parturition.
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Affiliation(s)
- Roberto Romero
- Perinatology Research Branch, National Institute of Child Health and Human Development, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland, USA.
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227
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Abstract
Antimicrobial peptides are ancient components of the innate immune system and have been isolated from organisms spanning the phylogenetic spectrum. Over an evolutionary time span, these peptides have retained potency, in the face of highly mutable target microorganisms. This fact suggests important coevolutionary influences in the host-pathogen relationship. Despite their diverse origins, the majority of antimicrobial peptides have common biophysical parameters that are likely essential for activity, including small size, cationicity, and amphipathicity. Although more than 900 different antimicrobial peptides have been characterized, most can be grouped as belonging to one of three structural classes: (1) linear, often of alpha-helical propensity; (2) cysteine stabilized, most commonly conforming to beta-sheet structure; and (3) those with one or more predominant amino acid residues, but variable in structure. Interestingly, these biophysical and structural features are retained in ribosomally as well as nonribosomally synthesized peptides. Therefore, it appears that a relatively limited set of physicochemical features is required for antimicrobial peptide efficacy against a broad spectrum of microbial pathogens. During the past several years, a number of themes have emerged within the field of antimicrobial peptide immunobiology. One developing area expands upon known microbicidal mechanisms of antimicrobial peptides to include targets beyond the plasma membrane. Examples include antimicrobial peptide activity involving structures such as extracellular polysaccharide and cell wall components, as well as the identification of an increasing number of intracellular targets. Additional areas of interest include an expanding recognition of antimicrobial peptide multifunctionality, and the identification of large antimicrobial proteins, and antimicrobial peptide or protein fragments derived thereof. The following discussion highlights such recent developments in antimicrobial peptide immunobiology, with an emphasis on the biophysical aspects of host-defense polypeptide action and mechanisms of microbial resistance.
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Affiliation(s)
- Nannette Y Yount
- Division of Infectious Diseases, Harbor-UCLA Medical Center, Torrance, CA 90509, USA
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228
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Khandelia H, Kaznessis YN. Structure of the antimicrobial beta-hairpin peptide protegrin-1 in a DLPC lipid bilayer investigated by molecular dynamics simulation. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2006; 1768:509-20. [PMID: 17254546 PMCID: PMC1855189 DOI: 10.1016/j.bbamem.2006.11.015] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2006] [Revised: 11/17/2006] [Accepted: 11/21/2006] [Indexed: 10/23/2022]
Abstract
All atom molecular dynamics simulations of the 18-residue beta-hairpin antimicrobial peptide protegrin-1 (PG-1, RGGRLCYCRRRFCVCVGR-NH(2)) in a fully hydrated dilauroylphosphatidylcholine (DLPC) lipid bilayer have been implemented. The goal of the reported work is to investigate the structure of the peptide in a membrane environment (previously solved only in solution [R.L. Fahrner, T. Dieckmann, S.S.L. Harwig, R.I. Lehrer, D. Eisenberg, J. Feigon, Solution structure of protegrin-1, a broad-spectrum antimicrobial peptide from porcine leukocytes. Chemistry and Biology, 3 (1996) 543-550]), and to delineate specific peptide-membrane interactions which are responsible for the peptide's membrane binding properties. A novel, previously unknown, "kick" shaped conformation of the peptide was detected, where a bend at the C-terminal beta-strand of the peptide caused the peptide backbone at residues 16-18 to extend perpendicular to the beta-hairpin plane. This bend was driven by a highly persistent hydrogen-bond between the polar peptide side-chain of TYR7 and the unshielded backbone carbonyl oxygen atom of GLY17. The H-bond formation relieves the unfavorable free energy of insertion of polar groups into the hydrophobic membrane core. PG-1 was anchored to the membrane by strong electrostatic binding of the protonated N-terminus of the peptide to the lipid head group phosphate anions. The orientation of the peptide in the membrane, and its influence on bilayer structural and dynamic properties are in excellent agreement with solid state NMR measurements [S. Yamaguchi, T. Hong, A. Waring, R.I. Lehrer, M. Hong, Solid-State NMR Investigations of Peptide-Lipid Interaction and Orientation of a b-Sheet Antimicrobial Peptide, Protegrin, Biochemistry, 41 (2002) 9852-9862]. Importantly, two simulations which started from different initial orientations of the peptide converged to the same final equilibrium orientation of the peptide relative to the bilayer. The kick-shaped conformation was observed only in one of the two simulations.
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Affiliation(s)
- Himanshu Khandelia
- Department of Chemical Engineering and Materials Science, University of Minnesota, 421, Washington Avenue SE, Minneapolis MN 55455, Minneapolis, Minnesota, U.S.A
| | - Yiannis N. Kaznessis
- Department of Chemical Engineering and Materials Science, University of Minnesota, 421, Washington Avenue SE, Minneapolis MN 55455, Minneapolis, Minnesota, U.S.A
- The Digital Technology Center, University of Minnesota, 421, Washington Avenue SE, Minneapolis MN 55455, Minneapolis, Minnesota, U.S.A
- Phone: +1-612-624-4197, Fax: +1-612-626-7246
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229
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Romero R, Espinoza J, Kusanovic JP, Gotsch F, Hassan S, Erez O, Chaiworapongsa T, Mazor M. The preterm parturition syndrome. BJOG 2006; 113 Suppl 3:17-42. [PMID: 17206962 PMCID: PMC7062298 DOI: 10.1111/j.1471-0528.2006.01120.x] [Citation(s) in RCA: 921] [Impact Index Per Article: 51.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The implicit paradigm that has governed the study and clinical management of preterm labour is that term and preterm parturition are the same processes, except for the gestational age at which they occur. Indeed, both share a common pathway composed of uterine contractility, cervical dilatation and activation of the membranes/decidua. This review explores the concept that while term labour results from physiological activation of the components of the common pathway, preterm labour arises from pathological signalling and activation of one or more components of the common pathway of parturition. The term "great obstetrical syndromes" has been coined to reframe the concept of obstetrical disease. Such syndromes are characterised by: (1) multiple aetiology; (2) long preclinical stage; (3) frequent fetal involvement; (4) clinical manifestations that are often adaptive in nature; and (5) gene-environment interactions that may predispose to the syndromes. This article reviews the evidence indicating that the pathological processes implicated in the preterm parturition syndrome include: (1) intrauterine infection/inflammation; (2) uterine ischaemia; (3) uterine overdistension; (4) abnormal allograft reaction; (5) allergy; (6) cervical insufficiency; and (7) hormonal disorders (progesterone related and corticotrophin-releasing factor related). The implications of this conceptual framework for the prevention, diagnosis, and treatment of preterm labour are discussed.
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Affiliation(s)
- R Romero
- Perinatology Research Branch, National Institute of Child Health and Human Development, NIH/DHHS, Bethesda, MD 20892, USA.
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230
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Lai JR, Epand RF, Weisblum B, Epand RM, Gellman SH. Roles of Salt and Conformation in the Biological and Physicochemical Behavior of Protegrin-1 and Designed Analogues: Correlation of Antimicrobial, Hemolytic, and Lipid Bilayer-Perturbing Activities. Biochemistry 2006; 45:15718-30. [PMID: 17176094 DOI: 10.1021/bi0617759] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Protegrins are short (16-18 residues) cationic peptides from porcine leukocytes that display potent, broad-spectrum antimicrobial activity. Protegrin-1 (PG-1), one of five natural homologues, adopts a rigid beta-hairpin structure that is stabilized by two disulfide bonds. We have previously employed the principles of beta-hairpin design to develop PG-1 variants that lack disulfide bonds but nevertheless display potent antimicrobial activity [Lai, J. R., Huck, B. R., Weisblum, B., and Gellman, S. H. (2002) Biochemistry 41, 12835-12842.]. The activity of these disulfide-free variants, however, is attenuated in the presence of salt, and the activity of PG-1 itself is not. Salt-induced inactivation of host-defense peptides, such as human defensins, is thought to be important in some pathological situations (e.g., cystic fibrosis), and the variation in salt-sensitivity among our PG-1 analogues offers a model system with which to explore the origins of these salt effects. We find that the variations in antimicrobial activity among our peptides are correlated with the folding propensities of these molecules and with the extent to which the peptides induce leakage of contents from synthetic liposomes. Comparable correlations were observed between folding and hemolytic activity. The extent to which added salt reduces antimicrobial activity parallels salt effects on vesicle perturbation, which suggests that the biological effects of high salt concentrations arise from modulation of peptide-membrane interactions.
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Affiliation(s)
- Jonathan R Lai
- Graduate Program in Biophysics, University of Wisconsin, Madison, Wisconsin 53706, USA
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231
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Mani R, Cady SD, Tang M, Waring AJ, Lehrer RI, Hong M. Membrane-dependent oligomeric structure and pore formation of a beta-hairpin antimicrobial peptide in lipid bilayers from solid-state NMR. Proc Natl Acad Sci U S A 2006; 103:16242-7. [PMID: 17060626 PMCID: PMC1637567 DOI: 10.1073/pnas.0605079103] [Citation(s) in RCA: 199] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We used solid-state NMR spectroscopy to investigate the oligomeric structure and insertion of protegrin-1 (PG-1), a beta-hairpin antimicrobial peptide, in lipid bilayers that mimic either the bacterial inner membrane [palmitoyloleoylphosphatidyl ethanolamine and palmitoyloleoylphosphatidylglycerol (POPE/POPG) bilayers] or the red blood cell membrane [neutral palmitoyloleoylphosphatidylcholine (POPC)/cholesterol bilayers]. (1)H spin diffusion from lipids to the peptide indicates that PG-1 contacts both the lipid acyl chains and the headgroups in the anionic membrane but resides far from the lipid chains in the POPC/cholesterol bilayer. (19)F spin diffusion data indicates that 75% of the beta-hairpins have homodimerized N strands and C strands in the anionic membrane. The resulting (NCCN)(n) multimer suggests a membrane-inserted beta-barrel enclosing a water pore. The lipids surrounding the beta-barrel have high orientational disorder and chain upturns, thus they may act as fillers for the pore. These results revise several features of the toroidal pore model, first proposed for magainin and subsequently applied to PG-1. In the POPC/cholesterol membrane, the N and C strands of PG-1 cluster into tetramers, suggesting the formation of beta-sheets on the membrane surface. Thus, the membrane composition plays a decisive role in defining the assembly and insertion of PG-1. The different oligomeric structures of PG-1 help to explain its greater toxicity for bacteria than for eukaryotic cells.
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Affiliation(s)
- Rajeswari Mani
- *Department of Chemistry, Iowa State University, Ames, IA 50011; and
| | - Sarah D. Cady
- *Department of Chemistry, Iowa State University, Ames, IA 50011; and
| | - Ming Tang
- *Department of Chemistry, Iowa State University, Ames, IA 50011; and
| | - Alan J. Waring
- Department of Medicine, University of California School of Medicine, Los Angeles, CA 90095
| | - Robert I. Lehrer
- Department of Medicine, University of California School of Medicine, Los Angeles, CA 90095
| | - Mei Hong
- *Department of Chemistry, Iowa State University, Ames, IA 50011; and
- To whom correspondence should be addressed. E-mail:
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232
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Kwakman PHS, te Velde AA, Vandenbroucke-Grauls CMJE, van Deventer SJH, Zaat SAJ. Treatment and prevention of Staphylococcus epidermidis experimental biomaterial-associated infection by bactericidal peptide 2. Antimicrob Agents Chemother 2006; 50:3977-83. [PMID: 17000746 PMCID: PMC1693978 DOI: 10.1128/aac.00575-06] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Biomaterial-associated infections (BAI) are the major cause of failure of indwelling medical devices and are predominantly caused by staphylococci, especially Staphylococcus epidermidis. We investigated the in vitro microbicidal activity of the synthetic antimicrobial peptide bactericidal peptide 2 (BP2) and its efficacy in a murine model of S. epidermidis BAI. BP2 showed potent microbicidal activity at micromolar concentrations against a broad spectrum of microorganisms, including antibiotic-resistant bacteria. The staphylocidal activity of BP2 was not affected by physiological salt concentrations and was only slightly affected by the presence of human plasma. In the BAI model, injection of BP2 (5 mg/kg of body weight) 1 h after challenge with S. epidermidis resulted in an 80% reduction in the number of culture-positive implants and a 100-fold reduction in survival of S. epidermidis in peri-implant tissue at 24 h postchallenge. When BP2 was injected along implants 3 h prior to bacterial challenge, the median numbers of CFU cultured from biomaterial implants and peri-implant tissue were reduced by 85% and 90%, respectively. In conclusion, BP2 has potent, broad-spectrum in vitro microbicidal activity and showed potent in vivo activity in a murine model of S. epidermidis biomaterial-associated infection.
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Affiliation(s)
- Paulus H S Kwakman
- Department of Medical Microbiology, Academic Medical Center, University of Amsterdam, The Netherlands
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233
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Chan DI, Prenner EJ, Vogel HJ. Tryptophan- and arginine-rich antimicrobial peptides: Structures and mechanisms of action. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2006; 1758:1184-202. [PMID: 16756942 DOI: 10.1016/j.bbamem.2006.04.006] [Citation(s) in RCA: 732] [Impact Index Per Article: 40.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2006] [Revised: 04/03/2006] [Accepted: 04/07/2006] [Indexed: 11/26/2022]
Abstract
Antimicrobial peptides encompass a number of different classes, including those that are rich in a particular amino acid. An important subset are peptides rich in Arg and Trp residues, such as indolicidin and tritrpticin, that have broad and potent antimicrobial activity. The importance of these two amino acids for antimicrobial activity was highlighted through the screening of a complete combinatorial library of hexapeptides. These residues possess some crucial chemical properties that make them suitable components of antimicrobial peptides. Trp has a distinct preference for the interfacial region of lipid bilayers, while Arg residues endow the peptides with cationic charges and hydrogen bonding properties necessary for interaction with the abundant anionic components of bacterial membranes. In combination, these two residues are capable of participating in cation-pi interactions, thereby facilitating enhanced peptide-membrane interactions. Trp sidechains are also implicated in peptide and protein folding in aqueous solution, where they contribute by maintaining native and nonnative hydrophobic contacts. This has been observed for the antimicrobial peptide from human lactoferrin, possibly restraining the peptide structure in a suitable conformation to interact with the bacterial membrane. These unique properties make the Arg- and Trp-rich antimicrobial peptides highly active even at very short peptide lengths. Moreover, they lead to structures for membrane-mimetic bound peptides that go far beyond regular alpha-helices and beta-sheet structures. In this review, the structures of a number of different Trp- and Arg-rich antimicrobial peptides are examined and some of the major mechanistic studies are presented.
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Affiliation(s)
- David I Chan
- Structural Biology Research Group, Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada T2N 1N4
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234
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Salditt T, Li C, Spaar A. Structure of antimicrobial peptides and lipid membranes probed by interface-sensitive X-ray scattering. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2006; 1758:1483-98. [DOI: 10.1016/j.bbamem.2006.08.002] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2006] [Revised: 08/04/2006] [Accepted: 08/04/2006] [Indexed: 10/24/2022]
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235
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236
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Bakás L, Chanturiya A, Herlax V, Zimmerberg J. Paradoxical lipid dependence of pores formed by the Escherichia coli alpha-hemolysin in planar phospholipid bilayer membranes. Biophys J 2006; 91:3748-55. [PMID: 16935953 PMCID: PMC1630460 DOI: 10.1529/biophysj.106.090019] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
alpha-Hemolysin (HlyA) is an extracellular protein toxin (117 kDa) secreted by Escherichia coli that targets the plasma membranes of eukaryotic cells. We studied the interaction of this toxin with membranes using planar phospholipid bilayers. For all lipid mixtures tested, addition of nanomolar concentrations of toxin resulted in an increase of membrane conductance and a decrease in membrane stability. HlyA decreased membrane lifetime up to three orders of magnitude in a voltage-dependent manner. Using a theory for lipidic pore formation, we analyzed these data to quantify how HlyA diminished the line tension of the membrane (i.e., the energy required to form the edge of a new pore). However, in contrast to the expectation that adding the positive curvature agent lysophosphatidylcholine would synergistically lower line tension, its addition significantly stabilized HlyA-treated membranes. HlyA also appeared to thicken bilayers to which it was added. We discuss these results in terms of models for proteolipidic pores.
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Affiliation(s)
- Laura Bakás
- Laboratory of Cellular and Molecular Biophysics, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
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237
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Kulagina NV, Shaffer KM, Anderson GP, Ligler FS, Taitt CR. Antimicrobial peptide-based array for Escherichia coli and Salmonella screening. Anal Chim Acta 2006; 575:9-15. [PMID: 17723565 DOI: 10.1016/j.aca.2006.05.082] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2006] [Revised: 05/12/2006] [Accepted: 05/22/2006] [Indexed: 11/23/2022]
Abstract
Numerous bacteria, plants, and higher organisms produce antimicrobial peptides (AMPs) as part of their innate immune system, providing a chemical defense mechanism against microbial invasion. Many AMPs exert their antimicrobial activity by binding to components of the microbe's surface and disrupting the membrane. The goal of this study was to incorporate AMPs into screening assays for detection of pathogenic species. Surface-immobilized AMPs such as polymyxins B and E could be used to detect Salmonella typhimurium and Escherichia coli O157:H7 in two assay formats: direct and sandwich. Both types of assay confirmed that the peptides were immobilized in active form and could bind cells in a concentration-dependent manner. Cell binding to the AMPs was peptide-density dependent. This method for monitoring pathogen binding was extended to include other cationic AMPs such as cecropin A, magainin I and parasin. Detection limits (LODs) for E. coli O157:H7 and S. typhimurium obtained with AMPs during sandwich assays were in the ranges of 5x10(4) to 5x10(5) and 1x10(5) to 5x10(6)cells mL(-1), respectively. The different AMPs showed significantly different affinities for the two bacterial species; the potential for classification of pathogens based on different binding patterns to AMPs is discussed.
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Affiliation(s)
- Nadezhda V Kulagina
- Center for Bio/Molecular Science & Engineering, Code 6900, Naval Research Laboratory, Washington, DC 20375-5348, USA
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238
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Tremouilhac P, Strandberg E, Wadhwani P, Ulrich AS. Synergistic transmembrane alignment of the antimicrobial heterodimer PGLa/magainin. J Biol Chem 2006; 281:32089-94. [PMID: 16877761 DOI: 10.1074/jbc.m604759200] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The antimicrobial activity of amphipathic alpha-helical peptides is usually attributed to the formation of pores in bacterial membranes, but direct structural information about such a membrane-bound state is sparse. Solid state (2)H-NMR has previously shown that the antimicrobial peptide PGLa undergoes a concentration-dependent realignment from a surface-bound S-state to a tilted T-state. The corresponding change in helix tilt angle from 98 to 125 degrees was interpreted as the formation of PGLa/magainin heterodimers residing on the bilayer surface. Under no conditions so far, has an upright membrane-inserted I-state been observed in which a transmembrane helix alignment would be expected. Here, we have demonstrated that PGLa is able to assume such an I-state in a 1:1 mixture with magainin 2 at a peptide-to-lipid ratio as low as 1:100 in dimyristoylphosphatidylcholine/dimyristoylphosphatidylglycerol model membranes. This (2)H-NMR analysis is based on seven orientational constraints from Ala-3,3,3-d(3) substituted in a non-perturbing manner for four native Ala residues as well as two Ile and one Gly. The observed helix tilt of 158 degrees is rationalized by the formation of heterodimers. This structurally synergistic effect between the two related peptides from the skin of Xenopus laevis correlates very well with their known functional synergistic mode of action. To our knowledge, this example of PGLa is the first case where an alpha-helical antimicrobial peptide is directly shown to assume a transmembrane state that is compatible with the postulated toroidal wormhole pore structure.
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Affiliation(s)
- Pierre Tremouilhac
- Institute for Biological Interfaces, Forschungszentrum Karlsruhe, 76344 Eggenstein-Leopoldshafen, Germany
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239
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Oard SV, Enright FM. Expression of the antimicrobial peptides in plants to control phytopathogenic bacteria and fungi. PLANT CELL REPORTS 2006; 25:561-72. [PMID: 16456649 DOI: 10.1007/s00299-005-0102-5] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2005] [Revised: 11/01/2005] [Accepted: 11/20/2005] [Indexed: 05/06/2023]
Abstract
Three antimicrobial peptides exhibiting in vitro antifungal activity were expressed in Arabidopsis to compare their in planta activity. Beta-Purothionin, cecropin B, and phor21 were expressed under an endogenous promoter with moderate-level activity and excreted extracellularly. Expression of beta-purothionin rendered the greatest antibacterial and antifungal resistance while cecropin B enhanced only antibacterial activity and phor21 did not improve antimicrobial resistance. The transgenic beta-purothionin arrested fungal growth on leaf surfaces and infection of stomata. Leaf extracts from plants producing beta-purothionin and cecropin B displayed membrane permeabilizing activity. The in planta antimicrobial activity of the tested peptides was consistent with previously reported in vitro experiments. The expression strategy allowed enhanced antifungal resistance without high-level transgene expression.
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Affiliation(s)
- S V Oard
- LSU AgCenter Biotechnology Laboratory, Louisiana State University, 115 Wilson Bldg., Baton Rouge, LA 70803, USA.
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240
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Wang W, Pan D, Song Y, Liu W, Yang L, Huang HW. Method of x-ray anomalous diffraction for lipid structures. Biophys J 2006; 91:736-43. [PMID: 16632507 PMCID: PMC1483071 DOI: 10.1529/biophysj.105.080267] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The structures of the unit cells of lipid phases that exhibit long-range crystalline order but short-range liquid-like disorder are of biological interests. In particular, the recently discovered rhombohedral phase has a unit cell containing either the structure of a membrane fusion intermediate state or that of a peptide-induced transmembrane pore, depending on the lipid composition and participating peptides. Diffraction from such systems generally presents a difficult phase problem. The existing methods of phase determination all have their limitations. Therefore it is of general interest to develop a new phasing method. The method of multi-wavelength anomalous dispersion is routinely used in protein crystallography, but the same method is difficult for lipid systems for the practical reason that the commonly used lipid samples for diffraction do not have a well-defined thickness. Here we describe a practical approach to use the multi-wavelength anomalous dispersion method for lipid structures. The procedure is demonstrated with the lamellar phase of a brominated lipid. The method is general to all phases as long as anomalous diffraction is applicable.
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Affiliation(s)
- Wangchen Wang
- Department of Physics & Astronomy, Rice University, Houston, Texas 77251, USA
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241
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Abstract
The kinetics of peptide-membrane association have been studied previously using stopped-flow tryptophan fluorescence; however, such experiments do not directly report the coil-to-helix transition process, which is a hallmark of peptide-membrane interaction. Herein, we report a new method for directly assessing the kinetics of the helix formation accompanied by the peptide-membrane association. This method is based on the technique of fluorescence resonance energy transfer (FRET) and an amino acid FRET pair, p-cyano-L-phenylalanine and tryptophan. To demonstrate the utility of this method, we have studied the membrane-mediated helix folding dynamics of a mutant of magainin 2, an antibiotic peptide found in the skin of the African clawed frog, Xenopus laevis. Our results indicate that the coil-to-helix transition occurs during the binding of the peptide to the lipid vesicle (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine/1-palmitoyl-2-oleoyl-sn-glycero-3-[phospho-rac-(1-glycerol)], 3:1, wt/wt) but prior to the full insertion of the peptide into the hydrophobic region of the lipid bilayers.
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Affiliation(s)
- Matthew J Tucker
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104, USA
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242
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Tremouilhac P, Strandberg E, Wadhwani P, Ulrich AS. Conditions affecting the re-alignment of the antimicrobial peptide PGLa in membranes as monitored by solid state 2H-NMR. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2006; 1758:1330-42. [PMID: 16716250 DOI: 10.1016/j.bbamem.2006.02.029] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2005] [Revised: 02/23/2006] [Accepted: 02/28/2006] [Indexed: 11/27/2022]
Abstract
The cationic antimicrobial peptide PGLa is electrostatically attracted to bacterial membranes, binds as an amphiphilic alpha-helix, and is thus able to permeabilize the lipid bilayer. Using solid state (2)H-NMR of non-perturbing Ala-d(3) labels on the peptide, we have characterized the helix alignment under a range of different conditions. Even at a very high peptide-to-lipid ratio (1:20) and in the presence of negatively charged lipids, there was no indication of a toroidal wormhole structure. Instead, PGLa re-aligns from a surface-bound S-state to an obliquely tilted T-state, which is presumably dimeric. An intermediate structure half-way between the S- and T-state was observed in fully hydrated multilamellar DMPC vesicles at 1:50, suggesting a fast exchange between the two states on the time scale of >50 kHz. We demonstrate that this equilibrium is shifted from the S- towards the T-state either upon (i) increasing the peptide concentration, (ii) adding negatively charged DMPG, or (iii) decreasing the level of hydration. The threshold concentration for re-alignment in DMPC is found to be between 1:200 and 1:100 in oriented samples at 96% humidity. In fully hydrated multilamellar DMPC vesicles, it shifts to an effective peptide-to-lipid ratio of 1:50 as some peptides are able to escape into the bulk water phase.
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Affiliation(s)
- Pierre Tremouilhac
- Institute for Biological Interfaces, Forschungszentrum Karlsruhe, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
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243
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Mode of action of the new antibiotic for Gram-positive pathogens daptomycin: comparison with cationic antimicrobial peptides and lipopeptides. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2006; 1758:1215-23. [PMID: 16615993 DOI: 10.1016/j.bbamem.2006.02.009] [Citation(s) in RCA: 312] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2005] [Revised: 02/01/2006] [Accepted: 02/02/2006] [Indexed: 11/26/2022]
Abstract
With the steady rise in the number of antibiotic-resistant Gram-positive pathogens, it has become increasingly important to find new antibacterial agents which are highly active and have novel and diversified mechanisms of action. Two classes will be discussed here: the cationic antimicrobial peptides, which are amphiphilic in nature, targeting membranes and increasing their permeability; and lipopeptides, which consist of linear or cyclic peptides with an N-terminus that is acylated with a fatty acid side chain. One member of the cyclic lipopeptide family, the anionic molecule daptomycin, has been extensively studied and is the major focus of this review. Models will be presented on its mode of action and comparisons will be made to the known modes of action of cationic antimicrobial peptides and other lipopeptides.
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244
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Molecular mechanism of antimicrobial peptides: the origin of cooperativity. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2006; 1758:1292-302. [PMID: 16542637 DOI: 10.1016/j.bbamem.2006.02.001] [Citation(s) in RCA: 356] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2005] [Revised: 01/29/2006] [Accepted: 02/01/2006] [Indexed: 10/25/2022]
Abstract
Based on very extensive studies on four peptides (alamethicin, melittin, magainin and protegrin), we propose a mechanism to explain the cooperativity exhibited by the activities of antimicrobial peptides, namely, a non-linear concentration dependence characterized by a threshold and a rapid rise to saturation as the concentration exceeds the threshold. We first review the structural basis of the mechanism. Experiments showed that peptide binding to lipid bilayers creates two distinct states depending on the bound-peptide to lipid ratio P/L. For P/L below a threshold P/L*, all of the peptide molecules are in the S state that has the following characteristics: (1) there are no pores in the membrane, (2) the axes of helical peptides are oriented parallel to the plane of membrane, and (3) the peptide causes membrane thinning in proportion to P/L. As P/L increases above P/L*, essentially all of the excessive peptide molecules occupy the I state that has the following characteristics: (1) transmembrane pores are detected in the membrane, (2) the axes of helical peptides are perpendicular to the plane of membrane, (3) the membrane thickness remains constant for P/L> or =P/L*. The free energy based on these two states agrees with the data quantitatively. The free energy also explains why lipids of positive curvature (lysoPC) facilitate and lipids of negative curvature (PE) inhibit pore formation.
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245
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Appelt C, Wessolowski A, Söderhäll JA, Dathe M, Schmieder P. Structure of the antimicrobial, cationic hexapeptide cyclo(RRWWRF) and its analogues in solution and bound to detergent micelles. Chembiochem 2006; 6:1654-62. [PMID: 16075425 DOI: 10.1002/cbic.200500095] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Antimicrobial, cationic peptides are abundant throughout nature as part of many organisms' defence against microorganisms. They exhibit a large variety of sequences and structural motifs and are thought to act by rupturing the bacterial membrane. Several models based on biophysical experiments have been proposed for their mechanism of action. Here we present the NMR-determined structure of the cyclic, cationic antimicrobial peptide cyclo(RRWWRF) both free in aqueous solution and bound to detergent micelles. The peptide has a rather flexible but ordered structure in water. A distinct structure is formed when the peptide is bound to a detergent micelle. The structures in neutral and negatively charged micelles are nearly identical but differ from that in aqueous solution. The orientation of the amino acid side chains creates an amphipathic molecule with the peptide backbone forming the hydrophilic part. The orientation of the peptide in the micelle was determined by using NOEs and paramagnetic agents. The peptide is oriented mainly parallel to the micelle surface in both detergents. Substitution of the arginine and tryptophan residues is known to influence the antimicrobial activity. Therefore the structure of the micelle-bound analogues cyclo(RRYYRF), cyclo(KKWWKF) and cyclo(RRNalNalRF) were also determined. They exhibit remarkable similarities in backbone conformation and side-chain orientation. The structure of these peptides allows the side-chain properties to be correlated to biological activity.
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Affiliation(s)
- Christian Appelt
- Forschungsinstitut für Molekulare Pharmakologie, Robert-Rössle-Strasse 10, 13125 Berlin, Germany
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246
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Yenugu S, Hamil KG, French FS, Hall SH. Antimicrobial Actions of Human and Macaque Sperm Associated Antigen (SPAG) 11 Isoforms: influence of the N-terminal peptide. Mol Cell Biochem 2006; 284:25-37. [PMID: 16411022 DOI: 10.1007/s11010-005-9009-2] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2005] [Accepted: 09/15/2005] [Indexed: 11/30/2022]
Abstract
In addition to their role in sperm maturation, recent evidence has indicated that epididymal proteins have a role in male reproductive tract innate immunity. Herein we demonstrate that human and macaque epididymal protein isoforms in the SPAG (sperm associated antigen) 11 family, full length SPAG11C, K and L exhibit potent antibacterial activity against E. coli. Analysis of activities of the N- and C-terminal domains revealed that the human N-terminal peptide is bactericidal, while the C-terminal domains that contain the defensin-like 6 cysteine array in SPAG11C and partial arrays in SPAG11K and SPAG11L, lack antibacterial activity. The N-terminal peptide does not appear to contain all the determinants of activity since full-length human SPAG11C is more active than the isolated N-terminal peptide and since sulfhydryl reduction and alkylation, which would affect primarily the C-terminal peptides, completely abolished activities of the whole proteins. These results suggest that the structure conferred by the disulfide bonds in human SPAG11C contributes to the antibacterial activity of the whole molecule. The activities of the N-terminal peptide and of full length human SPAG11C were somewhat reduced in increasing NaCl concentrations. In contrast, the antibacterial activities of full length macaque SPAG11C, K and L were unaffected by the presence of NaCl suggesting a mechanism in the macaque that is less dependent upon electrostatic interactions. SPAG11C, K and L disrupted E. coli membranes but had no effect on erythrocyte membranes. Inhibition of E. coli RNA, DNA and protein synthesis by nonlethal concentrations of SPAG11 isoforms indicated an additional mechanism of bacterial killing.
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Affiliation(s)
- Suresh Yenugu
- Laboratories for Reproductive Biology, Department of Pediatrics, University of North Carolina, Chapel Hill, 27599-7500, USA
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247
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Abstract
Here we report the design, synthesis and antibacterial activity of 20 lysine-peptoid hybrids. The hybrids are based on the peptoid lead structure [N-(1-naphthalenemethyl)glycyl]-[N-(4-methylbenzyl)glycyl]-[N-(1-naphthalenemethyl)glycyl]-N-(butyl)glycin amide (1) and contain between one and six lysine residues each. The compounds were tested for antibacterial activity against S. aureus ATCC 25923 and E. coli ATCC 25922. Furthermore, the hemolytic activity toward human erythrocytes was assessed. Several compounds with potent antibacterial activity and low hemolytic activity were identified.
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Affiliation(s)
- Trine S Ryge
- Department of Natural Sciences, Section of Bioorganic Chemistry, Royal Veterinary and Agricultural University, Copenhagen, Denmark
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248
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Jing W, Prenner EJ, Vogel HJ, Waring AJ, Lehrer RI, Lohner K. Headgroup structure and fatty acid chain length of the acidic phospholipids modulate the interaction of membrane mimetic vesicles with the antimicrobial peptide protegrin-1. J Pept Sci 2006; 11:735-43. [PMID: 16059971 DOI: 10.1002/psc.702] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The interaction of protegrin-1 (PG-1), a small beta-sheet antimicrobial peptide with acidic phospholipid model membranes was investigated by differential scanning calorimetry. We found that PG-1 can distinguish between liposomes of the anionic phospholipids DPPG, DPPS and DPPA, eventhough the headgroups of these phospholipids all have the same net charge and they carry the same hydrocarbon chains. Specifically, PG-1 had only a minor effect on the thermotropic phase behavior of DPPA liposomes, while it interacted preferentially with the fluid phase of DPPS. Furthermore, PG-1 could induce a phase separation in DPPG liposomes resulting in the formation of peptide-rich domains even at low concentrations of the peptide. However, this peptide-rich domain was not evident when the fatty acyl chains were longer or shorter by two carbon atoms. In addition, PG-1 can also form peptide-rich domains in DPPS vesicles but only at high concentrations of the peptide. These results suggest that in addition to an overall negative charge, the structural features of the phospholipid headgroups, lipid packing and thus membrane fluidity will influence the interaction with PG-1, thereby modulating its biological activity.
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Affiliation(s)
- Weiguo Jing
- Institute of Biophysics and X-ray Structure Research, Austrian Academy of Sciences, Graz
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249
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Langham AA, Khandelia H, Kaznessis YN. How can a β-sheet peptide be both a potent antimicrobial and harmfully toxic? Molecular dynamics simulations of protegrin-1 in micelles. Biopolymers 2006; 84:219-31. [PMID: 16235232 DOI: 10.1002/bip.20397] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
In this work, the naturally occurring beta-hairpin antimicrobial peptide protegrin-1 (PG-1) is studied by molecular dynamics simulation in all-atom sodium dodecylsulfate and dodecylphosphocholine micelles. These simulations provide a high-resolution picture of the interactions between the peptide and simple models of bacterial and mammalian membranes. Both micelles show significant disruption, as is expected for a peptide that is both active against bacteria and toxic to host cells. There is, however, clear differentiation between the behavior in SDS versus DPC, which suggests different mechanisms of interaction for PG-1 with mammalian and bacterial membranes. Specifically, the equilibrium orientation of the peptide relative to SDS is a mirror image of its position relative to DPC. In both systems, the arginine residues of PG-1 strongly interact with the head groups of the micelles. In DPC, the peptide prefers a location closer to the core of the micelle with Phe12, Val14, and Val16 imbedded in the core and the other side of the hairpin, which includes Leu5 and Tyr7, located closer to the surface of the micelle. In SDS, the peptide prefers a location at the micelle-water interface. The peptide position is reversed, with Leu5 and Cys6 imbedded furthest in the micelle core and Phe12, Val14, and Val16 on the surface of the micelle. We discuss the implications of these results with respect to activity and toxicity.
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Affiliation(s)
- Allison A Langham
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455, USA
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Danilova N. The evolution of immune mechanisms. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2006; 306:496-520. [PMID: 16619242 DOI: 10.1002/jez.b.21102] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
From early on in evolution, organisms have had to protect themselves from pathogens. Mechanisms for discriminating "self" from "non-self" evolved to accomplish this task, launching a long history of host-pathogen co-evolution. Evolution of mechanisms of immune defense has resulted in a variety of strategies. Even unicellular organisms have rich arsenals of mechanisms for protection, such as restriction endonucleases, antimicrobial peptides, and RNA interference. In multicellular organisms, specialized immune cells have evolved, capable of recognition, phagocytosis, and killing of foreign cells as well as removing their own cells changed by damage, senescence, infection, or cancer. Additional humoral factors, such as the complement cascade, have developed that co-operate with cellular immunity in fighting infection and maintaining homeostasis. Defensive mechanisms based on germline-encoded receptors constitute a system known as innate immunity. In jaw vertebrates, this system is supplemented with a second system, adaptive immunity, which in contrast to innate immunity is based on diversification of immune receptors and on immunological memory in each individual.Usually, each newly evolved defense mechanism did not replace the previous one, but supplemented it, resulting in a layered structure of the immune system. The immune system is not one system but rather a sophisticated network of various defensive mechanisms operating on different levels, ranging from mechanisms common for every cell in the body to specialized immune cells and responses at the level of the whole organism. Adaptive changes in pathogens have shaped the evolution of the immune system at all levels.
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Affiliation(s)
- Nadia Danilova
- Department of Molecular, Cell & Developmental Biology, University of California, Los Angeles, CA 90095-1606, USA.
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