1.
Structure-activity analysis of the dermcidin-derived peptide DCD 1L, an anionic antimicrobial peptide present in human sweat.
Source
University of Tuebingen, Germany;
Abstract
Dermcidin encodes the anionic amphiphilic peptide DCD 1L, which displays a broad spectrum of antimicrobial activity under conditions resembling those in human sweat. Here, we have investigated its mode of antimicrobial activity. We found that DCD 1L interacts preferentially with negatively charged bacterial phospholipids with a helix axis which is aligned flat on a lipid bilayer surface. Upon interaction with lipid bilayers DCD 1L forms oligomeric complexes which are stabilized by Zn2+. DCD-1L is able to form ion channels in the bacterial membrane and we propose that Zn2+-induced self-assembly of DCD 1L upon interaction with bacterial lipid bilayers is a prerequisite for ion channel formation. These data allow for the first time to propose a molecular model for the antimicrobial mechanism of a naturally processed human anionic peptide that is active under the harsh conditions present in human sweat.
- PMID:
- 22262861
- [PubMed - as supplied by publisher]
Roles of tRNA in cell wall biosynthesis.
Source
Department of Microbiology, Ohio State University, Columbus, OH, USA.
Abstract
Recent research into various aspects of bacterial metabolism such as cell wall and antibiotic synthesis, degradation pathways, cellular stress, and amino acid biosynthesis has elucidated roles of aminoacyl-transfer ribonucleic acid (aa-tRNA) outside of translation. Although the two enzyme families responsible for cell wall modifications, aminoacyl-phosphatidylglycerol synthases (aaPGSs) and Fem, were discovered some time ago, they have recently become of intense interest for their roles in the antimicrobial resistance of pathogenic microorganisms. The addition of positively charged amino acids to phosphatidylglycerol (PG) by aaPGSs neutralizes the lipid bilayer making the bacteria less susceptible to positively charged antimicrobial agents. Fem transferases utilize aa-tRNA to form peptide bridges that link strands of peptidoglycan. These bridges vary among the bacterial species in which they are present and play a role in resistance to antibiotics that target the cell wall. Additionally, the formation of truncated peptides results in shorterpeptide bridges and loss of branched linkages which makes bacteria more susceptible to antimicrobials. A greater understanding of the structure and substrate specificity of this diverse enzymatic family is necessary to aid current efforts in designing potential bactericidal agents. These two enzyme families are linked only by the substrate with which they modify the cell wall, aa-tRNA; their structure, cell wall modification processes and the physiological changes they impart on the bacterium differ greatly. WIREs RNA 2012. doi: 10.1002/wrna.1108 For further resources related to this article, please visit the WIREs website.
Copyright © 2012 John Wiley & Sons, Ltd.
- PMID:
- 22262511
- [PubMed - as supplied by publisher]
Metallopolymer-Peptide Hybrid Materials: Synthesis and Self-Assembly of Functional, Polyferrocenylsilane-Tetrapeptide Conjugates.
Source
School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS (UK), Fax: (+44) 117-925-1295, Fax: (+44) 117-929-0509.
Abstract
Conjugates of poly(ferrocenyldimethylsilane) (PFDMS) with Ac-(GA)(2) -OH, Ac-A(4) -OH, Ac-G(4) -OH and Ac-V(4) -OH have been prepared by reaction of the tetrapeptide units with the amino-terminated metallopolymer. The number average degree of polymerisation (DP(n) ) of the PFDMS was approximately 20 and comparable materials with shorter (DP(n) ≈10) and/or amorphous chains have been prepared by the same procedure. Poly(ferrocenylethylmethylsilane) (PFEMS) was employed for the latter purpose. All conjugates were characterised by GPC, MALDI-TOF MS, NMR and IR spectroscopy. With the exception of Ac-V(4) -PFDMS(20) , all materials exhibited some anti-parallel β-sheet structure in the solid state. The self-assembly of the conjugates was studied in toluene by DLS. The vast majority of the materials, irrespective of peptide sequence or chain crystallinity, afforded fibres consisting of a peptidic core surrounded by a PFS corona. These fibres were found in the form of cross-linked networks by TEM and AFM. The accessibility of the chemically reducing PFS corona has been demonstrated by the localised formation of silver nanoparticles on the surface of the fibres.
Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
- PMID:
- 22262498
- [PubMed - as supplied by publisher]
Exploiting cell surface thiols to enhance cellular uptake.
Source
Medical Research Council, Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, UK.
Abstract
Efficient cellular delivery is one of the key issues that has hampered the therapeutic development of novel synthetic biomolecules such as oligonucleotides, peptides and nanoparticles. The highly specialized cellular plasma membrane specifically internalizes compounds through tightly regulated mechanisms. It is possible to exploit these natural mechanisms of cellular uptake with rationally designed reagents. Here, we discuss how thiol groups (-SH) naturally present on the cell surface (exofacial thiols) can be used to enhance cellular association and internalization of various materials bearing thiol-reactive groups in their structure. We propose that such thiol modifications should be considered in future design of synthetic biomolecules for optimized cellular delivery.
Copyright © 2011 Elsevier Ltd. All rights reserved.
- PMID:
- 22260747
- [PubMed - as supplied by publisher]
Binding of a truncated form of Lecithin : retinol acyltransferase and its N- and C-terminal peptides to lipid monolayers.
Abstract
Lecithin retinol acyltransferase (LRAT) is a 230 amino acids membrane-associated protein which catalyzes the esterification of all-trans-retinol into all-trans-retinyl ester. A truncated form of LRAT (tLRAT), which contains the residues required for catalysis but which is lacking the N- and C-terminal hydrophobic segments, was produced to study its membrane binding properties. Measurements of the maximum insertion pressure of tLRAT, which is higher than the estimated lateral pressure of membranes, and the positive synergy factor a argue in favor of a strong binding of tLRAT to phospholipid monolayers. Moreover, the binding, secondary structure and orientation of the peptides corresponding to the N- and C-terminal hydrophobic segments of LRAT have been studied by circular dichroism and polarization-modulation infrared reflection absorption spectroscopy in monolayers. The results show that these peptidesspontaneously bind to lipid monolayers and adopt an alpha helical secondary structure. On the basis of these data, a new membrane topology model of LRAT is proposed where its N- and C-terminal segments allow to anchor this protein to the lipid bilayer.
- PMID:
- 22260449
- [PubMed - as supplied by publisher]
Food protein-derived bioactive peptides: production, processing, and potential health benefits.
Source
Authors are with Dept. of Human Nutritional Sciences and author Aluko is also with the Richardson Centre for Functional Foods and Nutraceuticals, Univ. of Manitoba, 196 Innovation Drive, Winnipeg, MB R3T 2N2, Canada. Author Udenigwe is also with Dept. of Food Science, Univ. of Guelph, Guelph, ON N1G 2W1, Canada. Direct inquiries to author Aluko (E-mail: alukor@cc.umanitoba.ca).
Abstract
Bioactive peptides (BAPs), derived through enzymatic hydrolysis of food proteins, have demonstrated potential for application as health-promoting agents against numerous human health and disease conditions, including cardiovascular disease, inflammation, and cancer. The feasibility of pharmacological application of these peptidesdepends on absorption and bioavailability in intact forms in target tissues, which in turn depends on structure of thepeptides. Therefore, production and processing of peptides based on important structure-function parameters can lead to the production of potent peptides. This article reviews the literature on BAPs with emphasis on strategic production and processing methods as well as antihypertensive, anticancer, anticalmodulin, hypocholesterolemic, and multifunctional properties of the food protein-derived peptides. It is recommended that future research efforts on BAP should be directed toward elucidation of their in vivo molecular mechanisms of action, safety at various doses, and pharmacological activity in maintaining homeostasis during aberrant health conditions in human subjects.
© 2011 Institute of Food Technologists®
- PMID:
- 22260122
- [PubMed - in process]
[Application of brain natriuretic peptide in evaluation of cardiac function in forensic medicine].
Source
School of Forensic Medicine, China Medical University, Shenyang 110001, China. shangyigaoweimin@126.com
Abstract
Brain natriuretic peptide (BNP) is a major marker for evaluating cardiac function and has been widely used in clinical practice. Recent researches show that BNP is also useful for identification of sudden cardiac death in forensic pathology. This article reviews the molecular structure and biological characteristics of the BNP and its application as a functional indicate in forensic medicine. It shows that the expression of BNP in cardiac muscles, together with the expression of BNP in blood and pericardium liquid can be used to evaluate the pathological physiology changes and dysfunction degrees of the heart during the cardiac sudden death.
- PMID:
- 22259867
- [PubMed - in process]
Cyclo-linopeptide B methanol tris-olvate.
Abstract
The title compound, C(56)H(83)N(9)O(9)S·3CH(3)OH, is a methanol tris-olvate of the cyclo-linopeptide cyclo(Met(1)-Leu(2)-Ile(3)-Pro(4)-Pro(5)-Phe(6)-Phe(7)-Val(8)-Ile(9)) (henceforth referred to as CLP-B), which was isolated from flaxseed oil. All the amino acid residues are in an l-configuration based on the CORN rule. The cyclic nona-peptideexhibits eight trans peptide bonds and one cis peptide bond observed between the two proline residues. The conformation is stabilized by an α-turn and two consecutive β-turns each containing a N-H⋯O hydrogen bond between the carbonyl group O atom of the first residue and the amide group H atom of the fourth (α-turn) or the third residue (β-turns), repectively. In the crystal, the components of the structure are linked by N-H⋯O and O-H⋯O hydrogen bonds into chains parallel to the a axis.
- PMID:
- 22259553
- [PubMed - in process]
Cultivation of Human Neural Progenitor Cells in a 3-dimensional Self-assembling Peptide Hydrogel.
Source
Albrecht-Kossel-Institute for Neuroregeneration, University of Rostock.
Abstract
The influence of 3-dimensional (3D) scaffolds on growth, proliferation and finally neuronal differentiation is of great interest in order to find new methods for cell-based and standardised therapies in neurological disorders or neurodegenerative diseases. 3D structures are expected to provide an environment much closer to the in vivo situation than 2D cultures. In the context of regenerative medicine, the combination of biomaterial scaffolds with neural stem and progenitor cells holds great promise as a therapeutic tool.(1-5) Culture systems emulating a three dimensional environment have been shown to influence proliferation and differentiation in different types of stem and progenitor cells. Herein, the formation and functionalisation of the 3D-microenviroment is important to determine the survival and fate of the embedded cells.(6-8) Here we used PuraMatrix(9,10) (RADA16, PM), a peptide based hydrogel scaffold, which is well described and used to study the influence of a 3D-environment on different cell types.(7,11-14) PuraMatrix can be customised easily and the synthetic fabrication of the nano-fibers provides a 3D-culture system of high reliability, which is in addition xeno-free. Recently we have studied the influence of the PM-concentration on the formation of the scaffold.(13) In this study the used concentrations of PM had a direct impact on the formation of the 3D-structure, which was demonstrated by atomic force microscopy. A subsequent analysis of the survival and differentiation of the hNPCs revealed an influence of the used concentrations of PM on the fate of the embedded cells. However, the analysis of survival or neuronal differentiation by means of immunofluorescence techniques posses some hurdles. To gain reliable data, one has to determine the total number of cells within a matrix to obtain the relative number of e.g. neuronal cells marked by βIII-tubulin. This prerequisites a technique to analyse the scaffolds in all 3-dimensions by a confocal microscope or a comparable technique like fluorescence microscopes able to take z-stacks of the specimen. Furthermore this kind of analysis is extremely time consuming. Here we demonstrate a method to release cells from the 3D-scaffolds for the later analysis e.g. by flow cytometry. In this protocol human neural progenitor cells (hNPCs) of the ReNcell VM cell line (Millipore USA) were cultured and differentiated in 3D-scaffolds consisting of PuraMatrix (PM) or PuraMatrix supplemented with laminin (PML). In our hands a PM-concentration of 0.25% was optimal for the cultivation of the cells(13), however the concentration might be adapted to other cell types.(12) The released cells can be used for e.g. immunocytochemical studies and subsequently analysed by flow cytometry. This speeds up the analysis and more over, the obtained data rest upon a wider base, improving the reliability of the data.
Retargeting of rat parvovirus H-1PV to cancer cells through genetic engineering of the viral capsid.
Source
Tumour Virology Division F010.
Abstract
The rat parvovirus H-1PV is a promising anticancer agent given its oncosuppressive properties and the absence of known side-effects in humans. H-1PV replicates preferentially in transformed cells, but the virus can enter both normal and cancer cells. Uptake by normal cells sequesters a significant portion of the administered viral dose, away from the tumour target. Hence, targeting H-1PV entry specifically to tumour cells is important to increase the efficacy of parvovirus-based treatments. In this study, we first found that sialic acid plays a key role in H-1PV entry. Then, we genetically engineered the H-1PV capsid in order to improve its affinity for human tumour cells. By analogy with the resolved crystal structure of the closely related parvovirus MVM, we developed an in silico 3D model of the H-1PV wild-type capsid. Based on this model, we identified putative amino acids involved in cell membrane recognition and virus entry at the level of the twofold axis of symmetry of the capsid, within the so-called "dimple" region. In situ mutagenesis of these residues significantly reduced binding and entry of H-1PV into permissive cells. We then engineered the entry-deficient viral capsid and inserted a cyclic RGD-4C peptide at the level of its threefold axis spike. This peptide binds α(v)β(3) and α(v)β(5) integrins, which are over-expressed in cancer cells and growing blood vessels. Insertion of thepeptide rescued viral infectivity towards cells over-expressing α(v)β(5) integrins resulting in efficient killing of these cells by the reengineered virus. This work demonstrates that H-1PV can be genetically retargeted through modification of its capsid, showing great promise for a more efficient use of this virus in cancer therapy.
Demonstration of α-Helical Structure of Peptides Tethered to Gold Surfaces Using Surface Infrared and Circular Dichroic Spectroscopies.
Abstract
Gold and quartz surfaces terminated in an alkane thiol self-assembled monolayer (SAM) that were partially terminated with azide were reacted with a helical peptide containing two alkyne groups in a Cu(I)-catalyzed Huisgen cycloaddition. Surface grazing incidence angle reflection-absorption infrared spectroscopy (GRAS-IR) was used to determine that when the Au surface was terminated with 25% of the monolayer containing azide groups, 92% of available azide groups reacted with the peptide. The majority of peptides reacted with both alkynes, resulting in peptides tethered to the surface through two covalent bonds. This was confirmed by comparison to a control peptide containing only one reactive alkyne group. Surface circular dichroic (CD) spectroscopy showed that while the helical structure of the peptide was distorted in the reaction solution, α-helical structure was induced when tethered on the SAM functionalized Au surface. Demonstration of the preservation of desired secondary structure of helical elements at a chemically functionalized surface is an important advance in preparing robust biologically mimetic surfaces to integrate functioning proteins into inorganic materials.
Immunological Evaluation of Lipopeptide Group A Streptococcus (GAS) Vaccine: Structure-Activity Relationship.
Source
The University of Queensland, School of Chemistry and Molecular Biosciences (SCMB), St. Lucia, Queensland, Australia.
Abstract
Streptococcus pyogenes (group A streptococcus, GAS) is a Gram-positive bacterial pathogen responsible for a wide variety of diseases. To date, GAS vaccine development has focused primarily on the M-protein. The M-protein is highly variable at the amino (N)-terminus (determining serotype) but is conserved at the carboxyl (C)-terminus. Previously a 29 amino acid peptide (named J14) from the conserved region of the M-protein was identified as a potential vaccine candidate. J14 was capable of eliciting protective antibodies that recognized many GAS serotypes when co-administered with immuno-stimulants. This minimal epitope however showed no immunogenicity when administered alone. In an attempt overcome this immunological non-responsiveness, we developed a self-adjuvanting vaccine candidate composed of three components: the B-cell epitope (J14), a universal helper T-cell epitope (P25) and a lipid moiety consisting of lipoamino acids (Laas) which target Toll-like receptor 2 (TLR2). Immunological evaluation in B10.BR (H-2k) mice demonstrated that the epitope attachment to the point of lipid moiety, and the length of the Laa alkyl chain have a profound effect on vaccine immunogenicity after intranasal administration. It was demonstrated that a vaccine featuring C-terminal lipid moiety containing alkyl chains of 16 carbons, with P25 located at the N-terminus, and J14 attached to the side chain of a central lysine residue was capable of inducing optimal antibody response. These findings have considerable relevance to the development of a broad spectrum J14-based GAS vaccine and in particular provided a rational basis for peptide vaccine design based on this self-adjuvanting lipopeptide technology.
Calcium/calmodulin-dependent protein kinase II (CaMKII) inhibition induces neurotoxicity via dysregulation of glutamate/calcium signaling and hyperexcitability.
Source
Indiana University School of Medicine, United States.
Abstract
Aberrant glutamate and calcium signaling are neurotoxic to specific neuronal populations. Calcium/calmodulin-dependent kinase II (CaMKII), a multifunctional serine/threonine protein kinase in neurons, is believed to regulate neurotransmission and synaptic plasticity in response to calcium signaling produced by neuronal activity. Importantly, several CaMKII substrates control neuronal structure, excitability, and plasticity. Here, we demonstrate that CaMKII inhibition for >4 hours using small molecule and peptide inhibitors induces apoptosis in cultured cortical neurons. The neuronal death produced by prolonged CaMKII inhibition is associated with an increase in TUNEL staining, caspase-3 cleavage, and is blocked with translation inhibitor cycloheximide. Thus, this neurotoxicity is consistent with apoptotic mechanisms, a conclusion that is further supported by dysregulated calcium signaling with CaMKII inhibition. CaMKII inhibitory peptides also enhance the number of action potentials generated by a ramp depolarization, suggesting increased neuronal excitability with a loss of CaMKII activity. Extracellular glutamate concentrations are augmented with prolonged inhibition of CaMKII. Enzymatic buffering of extracellular glutamate and antagonism of the NMDA subtype of glutamate receptors prevent the calcium dysregulation and neurotoxicity associated with prolonged CaMKII inhibition. However, in the absence of CaMKII inhibition, elevated glutamate levels do not induce neurotoxicity, suggesting that a combination of CaMKII inhibition and elevated extracellular glutamate levels results in neuronal death. In sum, the loss of CaMKII observed with multiple pathological states in the central nervous system, including epilepsy, brain trauma, and ischemia, likely exacerbates programmed cell death by sensitizing vulnerable neuronal populations to excitotoxic glutamate signaling and inducing an excitotoxic insult itself.
Roles of Hydrophobicity and Charge Distribution of Cationic AntimicrobialPeptides in Peptide-Membrane Interactions.
Source
Hospital for Sick Children, Toronto, Canada;
Abstract
Cationic antimicrobial peptides (CAPs) occur as important innate immunity agents in many organisms (including humans) and offer a viable alternative to conventional antibiotics as they physically disrupt the bacterial membranes, leading to membrane lysis and eventually cell death. In the present work, we studied the biophysical and microbiological characteristics of designed CAPs varying in hydrophobicity levels and charge distributions by a variety of biophysical and biochemical approaches, including in tandem atomic force microscopy (AFM) and attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), circular dichroism spectroscopy, and SDS-PAGE. Peptide structural properties were correlated with their membrane disruptive powers and antimicrobial activities. In bacterial lipid model membranes, a time-dependent increase of aggregated beta-strand-type structure in CAPs with relatively high hydrophobicity (such as KKKKKK-ALFALWLAFLA-NH2) was essentially absent in CAPs with lower hydrophobicity (such as KKKKKK-AAFAAWAAFAA-NH2). Re-distribution of positive charges by placing three Lys residues at both termini while maintaining identical sequences minimized self-aggregation above the dimer level. Peptides containing four Leu residues were destructive to mammalian model membranes, while those with corresponding Ala residues were not. This finding was mirrored in hemolysis studies in human erythrocytes, where Ala-only peptides displayed virtually no hemolysis up to 320 μM, but the four-Leu peptides induced 40-80% hemolysis in the same concentration range. Allpeptides studied displayed strong antimicrobial activity against Pseudomonas aeruginosa (MICs = 4-32 μM). The overall findings suggest optimal routes to balancing peptide hydrophobicity and charge distribution that allow efficient penetration and disruption of the bacterial membranes without damage to mammalian (host) membranes.
Orientation and depth of surfactant protein B C-terminal helix in lung surfactant bilayers.
Source
Université de Strasbourg/CNRS, UMR7177, Institut de Chimie, 4, rue Blaise Pascal, 67070 Strasbourg, France.
Abstract
SP-B(CTERM) is a cationic amphipathic helical peptide and functional fragment composed of residues 63 to 78 of surfactant protein B (SP-B). Static oriented and magic angle spinning solid state NMR, along with molecular dynamics simulation was used to investigate its structure, orientation, and depth in lipid bilayers of several compositions, namely POPC, DPPC, DPPC/POPC/POPG, and bovine lung surfactant extract (BLES). In all lipid environments the peptide was oriented parallel to the membrane surface. While maintaining this approximately planar orientation, SP-B(CTERM) exhibited a flexible topology controlled by subtle variations in lipid composition. SP-B(CTERM)-induced lipid realignment and/or conformational changes at the level of the head group were observed using (31)P solid-state NMR spectroscopy. Measurements of the depth of SP-B(CTERM) indicated the peptide center positions ~8Å more deeply than the phosphate headgroups, a topology that may allow the peptide to promote functional lipid structures without causing micellization upon compression.
Copyright © 2011. Published by Elsevier B.V.
Small surfactant-like peptides can drive soluble proteins into active aggregates.
Abstract
ABSTRACT:
BACKGROUND:
Inactive protein inclusion bodies occur commonly in Escherichia coli (E. coli) cells expressing heterologous proteins. Previously several independent groups have found that active protein aggregates or pseudo inclusion bodies can be induced by a fusion partner such as a cellulose binding domain from Clostridium cellulovorans (CBDclos) when expressed in E. coli. More recently we further showed that a short amphipathic helical octadecapeptide 18A (EWLKAFYEKVLEKLKELF) and a short beta structure peptide ELK16 (LELELKLKLELELKLK) have a similar property.
RESULTS:
In this work, we explored a third type of peptides, surfactant-like peptides, for performing such a "pulling-down" function. One or more of three such peptides (L6KD, L6K2, DKL6) were fused to the carboxyl termini of model proteins including Aspergillus fumigatus amadoriase II (AMA, all three peptides were used), Bacillus subtilis lipase A (LipA, only L6KD was used, hereinafter the same), Bacillus pumilus xylosidase (XynB), and green fluorescent protein (GFP), and expressed in E. coli. All fusions were found to predominantly accumulate in the insoluble fractions, with specific activities ranging from 25% to 92% of the native counterparts. Transmission electron microscopic (TEM) and confocal fluorescence microscopic analyses confirmed the formation of protein aggregates in the cell. Furthermore, binding assays with amyloid-specific dyes (thioflavin T and Cong red) to the AMA-L6KD aggregate and the TEM analysis of the aggregate following digestion with protease K suggested that the AMA-L6KD aggregate may contain structures reminiscent of amyloids, including a fibril-like structure core.
CONCLUSIONS:
This study shows that the surfactant-like peptides L6KD and it derivatives can act as a pull-down handler for converting soluble proteins into active aggregates, much like 18A and ELK16. These peptide-mediated protein aggregations might have important implications for protein aggregation in vivo, and can be explored for production of functional biopolymers with detergent or other interfacial activities.
Solution structure of native and recombinant expressed toxin CssII from the venom of the scorpion centruroides suffusus suffusus, and their effects on Nav1.5 Sodium channels.
Source
Instituto de Química, Departamento de Química de Biomacromoléculas, Universidad Nacional Autónoma de México, UNAM, Ciudad Universitaria, D.F., 04510, Mexico.
Abstract
The three-dimensional structures of the long-chain mammalian scorpion β-toxin CssII from Centruroides suffusus suffusus and of its recombinant form, HisrCssII, were determined by NMR. The neurotoxin CssII (nCssII) is a 66 amino acid long peptide with four disulfide bridges; it is the most abundant and deadly toxin from the venom of this scorpion. Both native and recombinant CssII structures were determined by nuclear magnetic resonance using a total of 828 sequential distance constraints derived from the volume integration of the cross peaks observed in 2D NOESY spectra. Both nCssII and HisrCssII structures display a mixed α/β fold stabilized by four disulfide bridges formed between pairs of cysteines: C1-C8, C2-C5, C3-C6, and C4-C7 (the numbers indicate the relative positions of the cysteine residues in the primary structure), with a distortion induced by two cis-prolines in its C-terminal part. The native CssII electrostatic surface was compared to both the recombinant one and to the Cn2 toxin, from the scorpion Centruroides noxius, which is also toxic to mammals. Structural features such N- and C-terminal differences could influence toxin specificity and affinity towards isoforms of different sub-types of Na(v) channels.
Copyright © 2012. Published by Elsevier B.V.
Dose-response effects of an antimicrobial peptide, a cecropin hybrid, on growth performance, nutrient utilisation, bacterial counts in the digesta and intestinal morphology in broilers.
Source
School of Life Science, Sun Yat-Sen University, Guangzhou 510275, People's Republic of China.
Abstract
The aim of the present study was to evaluate the feasibility of an antimicrobial peptide, cecropin A(1-11)-D(12-37)-Asn (CADN), as an alternative to antibiotic growth promoter (AGP) in poultry diets. A total of 1500 14-d-old indigenous male chickens (222 (sd 13) g) were randomly allocated to five groups with five replicate cages of sixty birds each, and fed ad libitum five grower diets and subsequently five finisher diets for 14 d each. The diets were made up by supplementing their basal diets with a CADN liquid sample (CADNL) at 0, 2, 4, 6 and 8 ml/kg, respectively. During the feeding period, a metabolic experiment was carried out to determine the apparent digestibility of diethyl ether extract, nitrogen retention and apparent metabolisable energy of the diet sample fed to each cage of chicks. At the end of the feeding experiment, one chick from each cage was killed for bacteriological, light microscopic and scanning electron microscopic examination of the intestinal villi. CADN had a negative linear, positive quadratic and negative linear effect on feed intake (F), weight gain (G) and feed:gain ratio (F:G), respectively, for the growers; it had a quadratic effect on F, G or F:G for the finishers; it increased nutrient utilisation for both growers and finishers; it decreased aerobic bacterial counts in both jejunal and caecal digesta in a dose-dependent manner; it enhanced intestinal villus heights in a dose-dependent manner and made the duodenum villi of the CADNL8 group at 42 d appear as a netted leaf-like structure. CADN is therefore a possible alternative to AGP in broiler feeds.
Influence of specific amino acid side-chains on the antimicrobial activity andstructure of bovine lactoferrampin (1) (1) This article is part of Special Issue entitled Lactoferrin and has undergone the Journal's usual peer review process.
Source
a University of Calgary, Department of Biological Sciences, 2500 University Drive NW, Calgary, AB T2N 1N4, Canada.
Abstract
Lactoferrin is an 80 kDa iron binding protein found in the secretory fluids of mammals and it plays a major role in host defence. An antimicrobial peptide, lactoferrampin, was identified through sequence analysis of bovine lactoferrin and its antimicrobial activity against a wide range of bacteria and yeast species is well documented. In the present work, the contribution of specific amino acid residues of lactoferrampin was examined to evaluate the role that they play in membrane binding and bilayer disruption. The structures of all the bovine lactoferrampin derivatives were examined with circular dichroism and nuclear magnetic resonance spectroscopy, and their interactions with phospholipids were evaluated with differential scanning calorimetry and isothermal titration calorimetry techniques. From our results it is apparent that the amphipathic N-terminal helix anchors the peptide to membranes with Trp 268 and Phe 278 playing important roles in determining the strength of the interaction and for inducing peptide folding. In addition, the N-terminal helix capping residues (DLI) increase the affinity for negatively charged vesicles and they mediate the depth of membrane insertion. Finally, the unique flexibility in the cationic C-terminal region of bovine lactoferrampin does not appear to be essential for the antimicrobial activity of the peptide.
Antimicrobial activity of peptides derived from human ß-amyloid precursor protein.
Source
Division of Dermatology and Venereology, Department of Clinical Sciences, Lund University, Biomedical Center, Tornavägen 10, SE-221 84, Lund, Sweden.
Abstract
Antimicrobial peptides are important effector molecules of the innate immune system. Here, we describe that peptidesderived from the heparin-binding disulfide-constrained loop region of human ß-amyloid precursor protein are antimicrobial. The peptides investigated were linear and cyclic forms of NWCKRGRKQCKTHPH (NWC15) as well as the cyclic form comprising the C-terminal hydrophobic amino acid extension FVIPY (NWCKRGRKQCKTHPHFVIPY; NWC20c). Compared with the benchmark antimicrobial peptide LL-37, these peptides efficiently killed the Gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa, the Gram-positive Staphylococcus aureus and Bacillus subtilis, and the fungi Candida albicans and Candida parapsilosis. Correspondingly, fluorescence and electron microscopy demonstrated that the peptides caused defects in bacterial membranes. Analogously, the peptidespermeabilised negatively charged liposomes. Despite their bactericidal effect, the peptides displayed very limited hemolytic activities within the concentration range investigated and exerted very small membrane permeabilising effects on human epithelial cells. The efficiency of the peptides with respect to bacterial killing and liposome membrane leakage was in the order NWC20c > NWC15c > NWC15l, which also correlated to the adsorption density for these peptides at the model lipid membrane. Thus, whereas the cationic sequence is a minimum determinant for antimicrobial action, a constrained loop-structure as well as a hydrophobic extension further contributes to membrane permeabilising activity of this region of amyloid precursor protein. Copyright © 2012 European Peptide Society and John Wiley & Sons, Ltd.
Copyright © 2012 European Peptide Society and John Wiley & Sons, Ltd.
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