Anoplin, a novel antimicrobial peptide from the venom of the solitary wasp Anoplius samariensis

Melectin: a novel antimicrobial peptide from the venom of the cleptoparasitic bee Melecta albifrons

A novel antimicrobial peptide designated melectin was isolated from the venom of the cleptoparasitic bee Melecta albifrons. Its primary sequence was established as H-Gly-Phe-Leu-Ser-Ile-Leu-Lys-Lys-Val-Leu-Pro-Lys-Val-Met-Ala-His-Met-Lys-NH(2) by Edman degradation and ESI-QTOF mass spectrometry. Synthetic melectin exhibited antimicrobial activity against both gram-positive and -negative bacteria and it degranulated rat peritoneal mast cells, but its hemolytic activity was low. The CD spectra of melectin measured in the presence of trifluoroethanol and sodium dodecyl sulfate showed a high content alpha-helices, which indicates that melectin can adopt an amphipathic alpha-helical secondary structure in an anisotropic environment such as the bacterial cell membrane. To envisage the role of the proline residue located in the middle of the peptide chain on biological activity and secondary structure, we prepared several melectin analogues in which the Pro11 residue was either replaced by other amino acid residues or was omitted. The results of biological testing suggest that a Pro kink in the alpha-helical structure of melectin plays an important role in selectivity for bacterial cells. In addition, a series of N- and C-terminal-shortened analogues was synthesized to examine which region of the peptide is related to antimicrobial activity.

Functional whole-colony screening method to identify antimicrobial peptides

A high throughput method for screening cDNA libraries has been developed to identify putative antimicrobial peptides (AMPs). It is based on a rapid dye inclusion assay for assessing antagonism of bacterial viability. Colonies are grown on a membrane on a permissive medium until full colony size is reached. The membrane, supporting the array of colonies, is transferred onto an inductive medium containing a vital dye. Upon expression of any antagonizing peptides, the cell membrane becomes compromised allowing dye infusion to permit visual identification of deleterious peptides. Our approach was validated by screening a synthetic oligonucleotide library expressed in Escherichia coli. A random oligonucleotide library, containing inserts of up to 75 nucleotides in length was constructed and expressed in E. coli. From a potential pool of 100000 peptides, in a single round of screening, three were found to be antimicrobial: L1, L3, and L8. Peptide L1 was shown to have a concentration-dependent bactericidal effect against Gram-negative E. coli and moderate biostatic activity against the Gram-positive bacteria Listeria monocytogenes. L8 was found to have bacteriostatic, and possibly bactericidal effect against E. coli, Pseudomonas aeruginosa and Salmonella typhimurium. These results validated this high throughput AMP identification assay based on filter bound colony array libraries and vital dye inclusion.

Decoralin, a novel linear cationic alpha-helical peptide from the venom of the solitary eumenine wasp Oreumenes decoratus

A novel peptide, decoralin, was isolated from the venom of the solitary eumenine wasp Oreumenes decoratus. Its sequence, Ser-Leu-Leu-Ser-Leu-Ile-Arg-Lys-Leu-Ile-Thr, was determined by Edman degradation and corroborated by solid-phase synthesis. This sequence has the characteristic features of linear cationic alpha-helical peptides; rich in hydrophobic and basic amino acids with no disulfide bond, and accordingly, it can be predicted to adopt an amphipathic alpha-helix secondary structure. In fact, the CD spectra of decoralin in the presence of TFE or SDS showed a high alpha-helical conformation content. In a biological evaluation, decoralin exhibited a significant broad-spectrum antimicrobial activity, and moderate mast cell degranulation and leishmanicidal activities, but showed virtually no hemolytic activity. A synthetic analog with C-terminal amidation showed a much more potent activity in all the biological assays.

Myotoxic effects of mastoparan from Polybia paulista (Hymenoptera, Epiponini) wasp venom in mice skeletal muscle

In a previous study, we showed that the Polybia paulista wasp venom causes strong myonecrosis. This study was undertaken to characterize the myotoxic potency of mastoparan (Polybia-MPII) isolated from venom (0.25 microg/microl) and injected in the tibial anterior (TA) muscle (i.m.) of Balb/c mice. The time course of the changes was followed at muscle degenerative (3 and 24h) and regenerative (3, 7, and 21 days) periods (n=6) after injection and compared to matched controls by calculation of the percentage of cross-sectional area affected and determination of creatine kinase (CK) activity (n=10). The results showed that although MP was strongly myotoxic, its capacity for regeneration was maintained high. Since the extent of tissue damage was not correlated with the CK serum levels, which remained very low, we raised the hypothesis that the enzyme underwent denaturation by the peptide. Evidence suggested that MP induced the death of TA fibers by necrosis and apoptosis and had the sarcolemma as its primordial target. Given its amphiphilic polycationic nature and based on the vast spectrum of functions attributed to the peptide, we suggest that MP interaction with cell membrane impaired the phosphorylation of dystrophin essential for sarcolemma mechanical stability, and disturbed Ca2+ mobilization with obvious implications on sarcoplasmic reticulum and mitochondrial functioning.

Structure--activity study of the antibacterial peptide fallaxin

Fallaxin is a 25-mer antibacterial peptide amide, which was recently isolated from the West Indian mountain chicken frog Leptodactylus fallax. Fallaxin has been shown to inhibit the growth of several Gram-negative bacteria including Enterobacter cloacae, Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa. Here, we report a structure-activity study of fallaxin based on 65 analogs, including a complete alanine scan and a full set of N- and C-terminal truncated analogs. The fallaxin analogs were tested for hemolytic activity and antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-intermediate resistant S. aureus, (VISA), methicillin-susceptible S. aureus (MSSA), E. coli, K. pneumoniae, and P. aeruginosa. We identified several analogs, which showed improved antibacterial activity compared to fallaxin. Our best candidate was FA12, which displayed MIC values of 3.12, 25, 25, and 50 muM against E. coli, K. pneumoniae, MSSA, and VISA, respectively. Furthermore, we correlated the antibacterial activity with various structural parameters such as charge, hydrophobicity H, mean hydrophobic moment mu(H), and alpha-helicity. We were able to group the active and inactive analogs according to mean hydrophobicity H and mean hydrophobic moment mu(H). Far-UV CD-spectroscopy experiments on fallaxin and several analogs in buffer, in TFE, and in membrane mimetic environments (small unilamellar vesicles) indicated that a coiled-coil conformation could be an important structural trait for antibacterial activity. This study provides data that support fallaxin analogs as promising lead structures in the development of new antibacterial agents.

Nanoanalysis of the arthropod neuro-toxins

Many kinds of venomous principles modulate physiological responses of mammalian signal transduction systems, on which they act selectively as enhancers, inhibitors or some other kind of effectors. These toxins become useful tools for physiological research. We have employed and characterized paralyzing toxins from the venom of spiders, insects and scorpions with a limited supply. We have developed rapid and sensitive mass spectrometric technology and applied for the identification of these toxins. Venom profiles are screened by MALDI-TOF fingerprinting analysis prior to purification of venomous components, then marked target toxins of small molecular mass (1000-5000) are characterized directly by means of mass spectrometric techniques such as Frit-FAB MS/MS, CID/PSD-TOF MS, Capil.-HPLC/Q-TOF MS/MS etc.

Eumenitin, a novel antimicrobial peptide from the venom of the solitary eumenine wasp Eumenes rubronotatus

A novel antimicrobial peptide, eumenitin, was isolated from the venom of the solitary eumenine wasp Eumenes rubronotatus. The sequence of eumenitin, Leu-Asn-Leu-Lys-Gly-Ile-Phe-Lys-Lys-Val-Ala-Ser-Leu-Leu-Thr, was mostly analyzed by mass spectrometry together with Edman degradation, and corroborated by solid-phase synthesis. This peptide has characteristic features of cationic linear alpha-helical antimicrobial peptides, and therefore, can be predicted to adopt an amphipathic alpha-helix secondary structure. In fact, the CD spectra of eumenitin in the presence of TFE or SDS showed a high content of alpha-helical conformation. Eumenitin exhibited inhibitory activity against both Gram-positive and Gram-negative bacteria, and moderately stimulated degranulation from the rat peritoneal mast cells and the RBL-2H3 cells, but showed no hemolytic activity against human erythrocytes. This antimicrobial peptide in the eumenine wasp venom may play a role in preventing potential infection by microorganisms during prey consumption by their larvae.

Potent antibacterial lysine-peptoid hybrids identified from a positional scanning combinatorial library

In this paper, we describe the synthesis and screening of a biased positional scanning library made up of peptoids (N-alkylglycines) and lysines. The library consisted of 100 mixtures divided into four sub-libraries; OXXXKKK, XOXXKKK, XXOXKKK, and XXXOKKK, O being a defined peptoid building block and X a mixture of 25 peptoid building blocks. A theoretical number of 390,625 compounds were synthesized. The compound mixtures were screened against the American Type Culture Collection (ATCC) Staphylococcus aureus ATCC 25923 and Escherichia coli ATCC 25922 bacterial strains, and the cytotoxic activities were assessed using a human blood hemolytic assay. The results from each sub-library were examined to identify the most potent amine at each position. On the basis of this knowledge eight new lysine-peptoid hybrids were synthesized and tested in the biological assays. One compound in particular, [N-(cyclohexylmethyl)glycyl]-[N-(1-methylhexyl)glycyl]-[N-(4-methylbenzyl)glycyl]-[N-(2-(3-chlorophenyl)ethyl)glycyl]-lysyl-lysyl-lysine amide, showed high antibacterial activity and low toxicity toward red blood cells.

In vivo and in vitro activity of venom from the endoparasitic wasp Pimpla turionellae (L.) (Hymenoptera: Ichneumonidae)

The biological activity of venom from Pimpla turionellae L. (Hymenoptera: Ichneumonidae) was examined in vivo toward larvae and pupae of Galleriae mellonella L. (Lepidoptera: Pyralidae), and in vitro toward bacterial and fungal cultures, as well as cultured insect cells. Pupae of G. mellonella were far more susceptible to the venom than larvae. At low doses of venom [0.1 venom reservoir equivalents (VRE)], pupal abdominal mobility was inhibited within 30 min, and by 24 h, all pupae injected with venom concentrations >0.5 VRE were completely paralyzed. These same doses of venom resulted in an inhibition of adult emergence. Host larvae were far less sensitive to wasp venom as evidenced by all venom injected larvae remaining responsive to mechanical stimulation by 1 h post injection, even at concentrations equivalent to 1 venom reservoir. Eventually (>2 h at 25 degrees C), venom-injected larvae became immobile, then flaccid, and all died within 24 h post-injection. At lower concentrations of wasp venom, the onset of paralysis was delayed by comparison to that evoked by 1 VRE, and few host larvae were able to pupate. Development of host larvae to adult emergence was also reduced in a dose-dependent manner, with eclosion completely prevented at high concentrations (>0.5 VRE) of venom. Venom doses <0.5 VRE did not appear to induce paralysis or alter larval development. When venom was incubated with bacterial or fungal cultures, no antimicrobial activity was detected. However, wasp venom was found to be cytotoxic and cytolytic to cultured cells derived from the cabbage looper Trichoplusia ni Hubner (Lepidoptera: Noctuidae) and the yellow fever mosquito, Aedes aegypti (L.) (Diptera: Culcidae). Though both cell types displayed similar susceptibility in terms of LC50s, the lepidopteran cells responded much more rapidly with regard to the onset of morphological changes and the timing of cell death. A possible mode of action for the venom is discussed.

Novel lysine-peptoid hybrids with antibacterial properties

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.

Structural and functional characterization of two novel peptide toxins isolated from the venom of the social wasp Polybia paulista

Two novel inflammatory peptides were isolated from the venom of the social wasp Polybia paulista. They had their molecular masses determined by ESI-MS and their primary sequences were elucidated by Edman degradation chemistry as: Polybia-MPI: I D W K K L L D A A K Q I L-NH2 (1654.09 Da), Polybia-CP: I L G T I L G L L K S L-NH2 (1239.73 Da). Both peptides were functionally characterized by using Wistar rat cells. Polybia-MPI is a mast cell lytic peptide, which causes no hemolysis to rat erythrocytes and presents chemotaxis for polymorphonucleated leukocytes (PMNL) and with potent antimicrobial action both against Gram-positive and Gram-negative bacteria. Polybia-CP was characterized as a chemotactic peptide for PMNL cells, presenting antimicrobial action against Gram-positive bacteria, but causing no hemolysis to rat erythrocytes and no mast cell degranulation activity at physiological concentrations.

Purification and characterization of a novel peptide with antifungal activity from Bothrops jararaca venom

Different peptides have been isolated from a wide range of animal species. It is has become increasingly clear that due to the development of antibiotic-resistant microbes, antibacterial and antifungal peptides have attracted the attention in recent years, in order to find new therapeutic agents. In this work, a novel peptide with high inhibitory activity against fungi growth have been isolated from the venom of the Brazilian snake Bothrops jararaca. A Sephacryl S-100 gel filtration column was employed for further separation of proteins. The FV fraction with high antifungal activity was named Pep5Bj, pooled and submitted to reverse-phase chromatography in HPLC. The fraction containing the isolated peptide inhibited the growth of different phytopathogenic fungi (Fusarium oxysporum and Colletotrichum lindemuthianum) and yeast (Candida albicans and Saccharomyces cerevisiae). The peptide minimal inhibitory concentration is comparable to other known antifungal peptides, like insect defensins and cecropins, found in the last years in a large diversity of animals. We investigate F. oxysporum cells membrane permeabilization using SYTOX Green uptake, an organic compound that fluoresces upon interaction with nucleic acids after penetration in cell with compromised plasma membranes. When viewed under fluorescence optical microscopy, F. oxysporum cells exposed to Pep5Bj display strong SYTOX Green fluorescence in the cytosol, especially in the nuclei. The SYTOX Green data suggested that this effect is related to membrane permeabilization. The molecular masses of this peptide was obtained by MALDI-TOF spectrometry and corresponded to 1370Da.

Structure-activity relationship study of anoplin

Anoplin is a decapeptide amide, GLLKRIKTLL-NH2 derived from the venom sac of the solitary spider wasp, Anoplius samariensis. It is active against Gram-positive and Gram-negative bacteria and is not hemolytic towards human erythrocytes. The present paper reports a structure-activity study of anoplin based on 37 analogues including an Ala-scan, C- and N-truncations, and single and multiple residue substitutions with various amino acids. The analogues were tested for antibacterial activity against both S. aureus ATCC 25923 and E. coli ATCC 25922, and several potent antibacterial analogues were identified. The cytotoxicity of the analogues against human erythrocytes was assessed in a hemolytic activity assay. The antibacterial activity and selectivity of the analogues against S. aureus and E. coli varied considerably, depending on the hydrophobicity and position of the various substituted amino acids. In certain cases the selectivity for Gram-positive and Gram-negative bacteria was either reversed or altogether eliminated. In addition, it was generally found that antibacterial activity coincided with hemolytic activity.

Small peptides, big world: biotechnological potential in neglected bioactive peptides from arthropod venoms

Until recently, a toxinologist's tasks involved the search for highly toxic or lethal toxins in animal venoms that could explain the harmful effects in clinically observed symptoms. Most of these toxins were put on evidence using a function to structure approach, in which a biological phenomena observation usually guided the isolation and characterization of the causative molecule. Paving this way, many toxins were promptly purified because of their readily observed effect. Nevertheless, small molecules with micro-effects that are not easily visualized can be relatively neglected or poorly studied. This situation has changed now with the advent of the sensitivity, resolution and accuracy of techniques such as mass spectrometry and proteomic approaches used in toxinology. Taking advantage of these methodologies, small peptides with 'newly exploited' biological activities such as vasoactive, hormone-like, antimicrobial and others have been recently given much more attention, enlarging the known repertoire of bioactive molecules found in animal venoms. This article aims to review current knowledge on small biologically active peptides (<3 kDa) found in arthropod venoms and discuss their potentialities as new drug candidates or therapeutic lead compounds.

Structural and biological characterization of three novel mastoparan peptides from the venom of the neotropical social wasp Protopolybia exigua (Saussure)

The venom of the Neotropical social wasp Protopolybia exigua(Saussure) was fractionated by RP-HPLC resulting in the elution of 20 fractions. The homogeneity of the preparations were checked out by using ESI-MS analysis and the fractions 15, 17 and 19 (eluted at the most hydrophobic conditions) were enough pure to be sequenced by Edman degradation chemistry, resulting in the following sequences: Protopolybia MPI I-N-W-L-K-L-G-K-K-V-S-A-I-L-NH2 Protopolybia-MP II I-N-W-K-A-I-I-E-A-A-K-Q-A-L-NH2 Protopolybia-MP III I-N-W-L-K-L-G-K-A-V-I-D-A-L-NH2 All the peptides were manually synthesized on-solid phase and functionally characterized. Protopolybia-MP I is a hemolytic mastoparan, probably acting on mast cells by assembling in plasma membrane, resulting in pore formation; meanwhile, the peptides Protopolybia-MP II and -MP III were characterized as a non-hemolytic mast cell degranulator toxins, which apparently act by virtue of their binding to G-protein receptor, activating the mast cell degranulation.

Structural and functional characterization of N-terminally blocked peptides isolated from the venom of the social wasp Polybia paulista

Two novel peptides were isolated from the crude venom of the social wasp Polybia paulista, by using RP-HPLC under a gradient of MeCN from 5 to 60% (v/v) and named Polybine-I and -II. Further purification of these peptides under normal phase chromatography, rendered pure enough preparations to be sequenced by Edman degradation chemistry. However, both peptides did not interact with phenylisothiocyanate reagent, suggesting the existence of a chemically blocked N-terminus. Therefore, the sequences of both peptides were assigned by ESI-MS/MS under CID conditions, as follows: Polybine-I Ac-SADLVKKIWDNPAL-NH2 (Mr 1610 Da) and Polybine-II Ac-SVDMVMKGLKIWPL-NH2 (Mr 1657 Da). During the tandem mass spectrometry experiments, a loss of 43 a.m.u. was observed from the N-terminal residue of each peptide, suggesting the acetylation of the N-terminus. Subsequently, the peptides with and without acetylation were synthesized on solid phase and submitted to functional characterizations; the biological activities investigated were: hemolysis, chemotaxis of polymorphonucleated leukocytes (PMNL), mast cell degranulation and antibiosis. The results revealed that the acetylated peptides exhibited more pronounced chemotaxis of PMNL cells and mast cell degranulation than the respective non-acetylated congeners; no hemolytic and antibiotic activities were observed, irrespective to the blockage or not of the alpha-amino groups of the N-terminal residues of each peptide. Therefore, the N-terminal acetylation may be related to the increase of the inflammatory activity of both peptides.

Structural and biological characterization of two novel peptides from the venom of the neotropical social wasp Agelaia pallipes pallipes

The venom of the neotropical social wasp Agelaia pallipes pallipes was fractionated by RP-HPLC resulting in the elution of seven fractions; the last two were re-fractionated under RP-HPLC by using isocratic elution conditions and the purity of the fractions were confirmed by using ESI-MS analysis. Both fractions are constituted of peptide components, which were sequenced by Edman degradation chemistry, resulting in the following sequences: Protonectin I-L-G-T-I-L-G-L-L-K-G-L-NH(2). Agelaia-MP I-N-W-L-K-L-G-K-A-I-I-D-A-L-NH(2). Both peptides are manually synthesized on solid-phase and functionally characterized by using Wistar rats cells. Protonectin is a non-hemolytic chemotactic peptide for polymorphonucleated leukocytes (PMNL), presenting some mast cell degranulating activity and potent antimicrobial action both against Gram-positive and Gram-negative bacteria. Agelaia-MP was characterized as a hemolytic mast cell degranulator toxin, presenting a poor antimicrobial action and no chemotaxis for PMNL.

How C-Terminal Carboxyamidation Alters the Biological Activity of Peptides from the Venom of the Eumenine Solitary Wasp

Inflammatory peptides display different types of post-transcriptional modifications, such as C-terminal amidation, that alter their biological activity. Here we describe the structural and molecular dynamics features of the mast cell degranulating peptide, eumenine mastoparan-AF (EMP-AF-NH(2)), found in the venom of the solitary wasp, and of its carboxyl-free C-terminal form (EMP-AF-COO(-)) characterized by a reduced activity. Circular dichroism indicates that both peptides switch from a random coil conformation in water to a helical structure in TFE and SDS micelles. NMR data, in 30% TFE, reveal that the two peptides fold into an alpha-helix spanning most of their length, while they differ in terms of molecular rigidity. To understand the origins of the conformational flexibility observed in the case of EMP-AF-COO(-), a 5 ns MD simulation was carried out for each peptide, in an explicit water/TFE environment. The results show that the two peptides differ in an H-bond between Leu14 NH(2) and the backbone carbonyl of Ile11. The loss of that H-bond in EMP-AF-COO(-) leads to a significant modification of its structural dynamics. In fact, as evidenced by essential dynamics analysis, while EMP-AF-NH(2) exists mainly as a rigid structure, EMP-AF-COO(-) presents two helical stretches that fluctuate in some sort of independent fashion. We conclude that the diverse biological activity of the two peptides is not simply due to the reduction of the net positive charge, as generally suggested, but also to a structural perturbation of the amphipathic alpha-helix that affects their ability to perturb the cell membrane.

Antibacterial and proteolytic activity in venom from the endoparasitic wasp Pimpla hypochondriaca (Hymenoptera: Ichneumonidae)

Venom from the endoparasitic wasp, Pimpla hypochondriaca, is composed of a mixture of high and low molecular weight proteins, possesses phenoloxidase activity, has immunosuppressive properties, and induces paralysis in several insect species. In the present study we demonstrate that P. hypochondriaca venom also contains antibacterial and proteolytic activity. Antibacterial activity was detected against the Gram-negative bacteria Escherichia coli and Xanthamonas campestris but not against Pseudomonas syringae nor against two Gram-positive bacteria, Bacillus cereus and Bacillus subtilis. Endopeptidase and aminopeptidase activity in venom was detected using the synthetic fluorogenic substrates N-t-BOC-Phe-Ser-Arg-AMC, Arg-AMC and Leu-Arg. The aminopeptidase activity towards Arg-AMC was sensitive to amastatin (70% inhibition), an aminopeptidase inhibitor. Angiotensin-converting enzyme (ACE)-like enzyme activity was detected, by reverse-phase HPLC using the synthetic tripeptide Hip-His-Leu as a substrate. This activity was sensitive to captopril, an ACE inhibitor (IC(50) 3.8 x 10(-8) M). Using an antiserum raised against recombinant Drosophila melanogaster ACE-like enzyme, (rAnce), Western blot analysis revealed an immunoreactive protein, with a molecular weight estimate of 74 kDa, in P. hypochondriaca venom. The possibility that the endopeptidase, aminopeptidase and ACE are involved in the processing of peptide precursors in the venom sac is discussed.

Antibacterial and antifungal properties of alpha-helical, cationic peptides in the venom of scorpions from southern Africa

Two novel pore-forming peptides have been isolated from the venom of the South-African scorpion Opistophtalmus carinatus. These peptides, designated opistoporin 1 and 2, differ by only one amino acid and belong to a group of alpha-helical, cationic peptides. For the first time, a comparison of the primary structures of alpha-helical pore-forming peptides from scorpion venom was undertaken. This analysis revealed that peptides in the range of 40-50 amino acids contain a typical scorpion conserved sequence S(x)3KxWxS(x)5L. An extensive study of biological activity of synthesized opistoporin 1 and parabutoporin, a pore-forming peptide previously isolated from the venom of the South-African scorpion Parabuthus schlechteri, was undertaken to investigate an eventual cell-selective effect of the peptides. Opistoporin 1 and parabutoporin were most active in inhibiting growth of Gram-negative bacteria (1.3-25 micro m), while melittin and mastoparan, two well-known cytolytic peptides, were more effective against Gram-positive bacteria in the same concentration range. In addition, the peptides showed synergistic activity with some antibiotics commonly used in therapy. Opistoporin 1 and parabutoporin had hemolytic activity intermediate between the least potent mastoparan and the highly lytic melittin. Furthermore, all peptides inhibited growth of fungi. Experiments with SYTOX green suggested that this effect is related to membrane permeabilization.

Cupiennin 1d*: the cytolytic activity depends on the hydrophobic N-terminus and is modulated by the polar C-terminus

To investigate structural features modulating the biological activity of cupiennin 1 peptides from the spider Cupiennius salei, three truncated cupiennin 1d analogs were synthesized. The fact that their growth inhibiting effect on Gram-negative and Gram-positive bacteria, their lytic activity with human red blood cells and their insecticidal effect on Drosophila melanogaster correlates with structural properties shows that the hydrophobic N-terminal chain segment includes the major determinants of structure and activity. The polar C-terminus seems to modulate peptide accumulation at negatively charged cell surfaces via electrostatic interactions and has no important effect on the peptides' amphipathic secondary structure.

IsCT, a novel cytotoxic linear peptide from scorpion Opisthacanthus madagascariensis

A novel cytotoxic linear peptide, IsCT, was characterized from scorpion Opisthacanthus madagascariensis. It is a linear peptide with a molecular weight of 1501.9 Da composed of 13 amino acid residues without cysteines. MS/MS analysis showed that its C-terminal is amidated. The identity of IsCT is re-confirmed by comparing the chemical synthesized peptide with the natural one. IsCT demonstrated antimicrobial activity against both gram-positive and gram-negative bacteria and hemolytic activity to sheep red blood cells. Also, it can release histamine from rat peritoneal mast cells. The CD absorption suggested that IsCT had an alpha-helix configuration in aqueous TFE. IsCT is one of the shortest natural cytotoxic peptides described, and it will be a suitable model for studying peptide-lipid interactions.