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

Structural and biological characterization of mastoparans in the venom of Vespa species in Taiwan

Mastoparans, a family of small peptides, are isolated from the wasp venom. In this study, six mastoparans were identified in the venom of six Vespa species in Taiwan. The precursors of these mastoparans are composed of N-terminal signal sequence, prosequence, mature mastoparan, and appendix glycine at C-terminus. These mature mastoparans all have characteristic features of linear cationic peptides rich in hydrophobic and basic amino acids without disulfide bond. Therefore, these peptides could be predicted to adopt an amphipathic α-helical secondary structure. In fact, the CD (circular dichroism) spectra of these peptides show a high content α-helical conformation in the presence of 8 mM SDS or 40% 2,2,2-trifluoroethanol (TFE). All mastoparans exhibit mast cell degranulation activity, antimicrobial activity against both Gram-positive and -negative bacteria tested, various degree of hemolytic activity on chicken, human, and sheep erythrocytes as well as membrane permeabilization on Escherichia coli BL21. Our results also show that the hemolytic activity of mastoparans is correlated to mean hydrophobicity and mean hydrophobic moment.

Metal-binding dependent disruption of membranes by designed helices

The de novo design of molecular switching peptides is of increasing interest because it tests and extends our fundamental understanding of this process while laying the groundwork for the creation of new chemical and biological sensors. Here, an alpha-helical amphiphilic cell-lytic peptide, mastoparan X, was engineered to bind divalent cations. Binding of Zn(II) or Ni(II) to the designed peptide Mst-HH stabilizes the lytic amphiphilic structure and increases the activity of the peptide. Although both Zn(II) and Ni(II) activate Mst-HH for membrane lysis, they appear to do so via different mechanisms. Additionally, a series of metal binding-site mutants were synthesized to assess the relationship of charge and helical propensity to the toxicity and switchability. Additionally, by changing the characteristics of the metal-binding ligands, we can vary the selectivity of the site.

Melectin MAPs: the influence of dendrimerization on antimicrobial and hemolytic activity

The recently described antimicrobial peptide melectin (MEP, GFLSILKKVLPKVMAHMK-NH2) exhibits high antimicrobial activity against Gram-positive and Gram-negative bacteria. Here we describe the synthesis and biological activities of 23 new analogues of MEP. We studied the influence of dimerization and tetramerization (MAP-constructs of MEP) on the antimicrobial and hemolytic activities, as well as the role of Met in positions 14 and 17 of the peptide chain. Oxidation of the Met to Met(O) and Met(O2) decreases antimicrobial activity of all tested bacteria if the peptide is in the monomeric form, however, only to Staphylococcus aureus if in the form of dimer or tetramer. Dimerization and tetramerization increase the undesirable hemolytic activity of the peptides. Interestingly, substitution of Leu for Val in position 6 leads to the decrease of hemolytic activity. Introduction of the isosteric amino acid Nle into positions 14 or 17 or both leads to slight increase of hemolytic activity under preservation of high antimicrobial activities. Unfortunately, dimerization again leads to an increase of hemolytic activity.

Investigating the effect of different positioning of lysine residues along the peptide chain of mastoparans for their secondary structures and biological activities

In order to investigate the effect of the different positions of the positive charges generated by the ionization of the side-chain of lysine residues, on the structure-activity relationship of the mastoparans, the peptides Protonectarina-MP (INWKALLDAAKKVL-NH2), Parapolybia-MP (INWKKMAATALKMI-NH2) and Asn-2-Polybia-MP I (INWKKLLDAAKQIL-NH2) and MK-578 (INWLKAKKVAGMIL-NH2) were investigated as models. Thus, the four peptides had their secondary structure studied and were submitted to assays of mast cell degranulation, hemolysis, and antibiosis. The results of the bioassays made clear that those peptides bearing the positive charges positioned at the positions 4/5 and/or from 11 to 13 are the most active ones; meanwhile, the localization of the positive charges in the middle of peptide chain resulted in a poorly active peptide. Thus, Protonectarina-MP, Parapolybia-MP, and Asn-2-Polybia-MP I presented physiologically important hemolysis and antibiosis, while MK-578 presented only a reduced antibiotic activity. Circular dichroism analysis were carried-out in different environments revealing that the anionic environment of a mixture of phosphatidylcholine and phosphatidylglycerol (70:30) liposomes favored the higher helical content of the four peptides in this study in relation to the zwiterionic environment of 100% phosphatidylcholine liposomes. The positioning of the lysine residues at the strategic positions (4/5 and 11-13), flanking and maintaining stable α-helix which extends from the 4th to the 13th residue along the peptide chain, seems to contribute to maximal lytic efficiency of the mastoparans, which in turn results in a more homogeneous hydrophobic surface in the amphipathic structure.

Characterization of two novel polyfunctional mastoparan peptides from the venom of the social wasp Polybia paulista

Hymenoptera venoms are complex mixtures of biochemically and pharmacologically active components such as biogenic amines, peptides and proteins. Polycationic peptides generally constitute the largest group of Hymenoptera venom toxins, and the mastoparans constitute the most abundant and important class of peptides in the venom of social wasps. These toxins are responsible for histamine release from mast cells, serotonin from platelets, and catecholamines and adenylic acids from adrenal chromafin cells. The present work reports the structural and functional characterization of two novel mastoparan peptides identified from the venom of the neotropical social wasp Polybia paulista. The mastoparans Polybia-MP-II and -III were purified, sequenced and synthesized on solid phase using Fmoc chemistry and the synthetic peptides used for structural and functional characterizations. Polybia-MP-II and -III are tetradecapeptides, amidated at their C-termini, and form amphipathic alpha-helical conformations under membrane-mimetic conditions. Both peptides were polyfunctional, causing pronounced cell lysis of rat mast cells and erythrocytes, in addition to having antimicrobial activity against both Gram-positive and Gram-negative bacteria.

A novel serine protease inhibitor from the venom of Vespa bicolor Fabricius

Hornets possess highly toxic venoms, which are rich in toxin, enzymes and biologically active peptides. Many bioactive substances have been identified from wasp venoms but only a few serine protease inhibitors have been identified from two kinds of wasp venoms. In this work, a serine protease inhibitor named bicolin was purified and characterized from the venom of the wasp, Vespa bicolor Fabricius. The precursor encoding bicolin was cloned from the cDNA library of the venomous glands. It is a cysteine-rich small protein containing 54 amino acid residues including 6 half-cysteines. The peptide is homologous to serine protease inhibitors isolated from venoms of Anoplius samariensis and Pimpla hypochondriaca. Bicolin showed inhibitory ability against trypsin and thrombin.

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.

Antimicrobial peptides from the venoms of Vespa bicolor Fabricius

Hornets possess highly toxic venoms, which are rich in toxins, enzymes and biologically active peptides. Many bioactive substances have been identified from wasp venoms. Vespa mastoparan (MP-VBs) and Vespa chemotatic peptide presenting antimicrobial action (VESP-VBs) were purified and characterized from the venom of the wasp, Vespa bicolor Fabricius. The precursors encoding VESP-VBs and MP-VBs were cloned from the cDNA library of the venomous glands. Analyzed by FAB-MS, the amino acid sequence and molecular mass for VESP-VB1 were FMPIIGRLMSGSL and 1420.6, for MP-VB1 were INMKASAAVAKKLL and 1456.5, respectively. The primary structures of these peptides are homologous to those of chemotactic peptides and mastoparans isolated from other vespid venoms. These peptides showed strong antimicrobial activities against bacteria and fungi and induced mast cell degranulation, but displayed almost no hemolytic activity towards human blood red cells.

New potent antimicrobial peptides from the venom of Polistinae wasps and their analogs

Four new peptides of the mastoparan family, characterized recently in the venom of three neotropical social wasps collected in the Dominican Republic, Polistes major major, Polistes dorsalis dorsalis and Mischocyttarus phthisicus were synthesized and tested for antimicrobial potency against Bacillus subtilis, Staphylococcus aureus, Escherichia coli (E.c.) and Pseudomonas aeruginosa, and for hemolytic and mast cells degranulation activities. As these peptides possess strong antimicrobial activity (minimal inhibitory concentration (MIC) values against Bacillus subtillis and E.c. in the range of 5-40 microM), we prepared 40 of their analogs to correlate biological activities, especially antimicrobial, with the net positive charge, hydrophobicity, amphipathicity, peptide length, amino acid substitutions at different positions of the peptide chain, N-terminal acylation and C-terminal deamidation. Circular dichroism spectra of the peptides measured in the presence of trifluoroethanol or SDS showed that the peptides might adopt alpha-helical conformation in such anisotropic environments.

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.

Identification of three novel peptides isolated from the venom of the neotropical social waspPolistes major major

Three novel peptides designated as PMM1, PMM2, and PMM3 were isolated and characterized from the venom of the social wasp Polistes major major, one of the most common wasps in the Dominican Republic. By Edman degradation, and MALDI-TOF and ESI-QTOF mass spectrometry, the primary sequences of these peptides were established as follows: PMM1, H-Lys-Arg-Arg-Pro-Pro-Gly-Phe-Thr-Pro-Phe-Arg-OH (1357.77 Da); PMM2, H-Ile-Asn-Trp-Lys-Lys-Ile-Ala-Ser-Ile-Gly-Lys-Glu-Val-Leu-Lys-Ala-Leu-NH2 (1909.19 Da); and PMM3, H-Phe-Leu-Ser-Ala-Leu-Leu-Gly-Met-Leu-Lys-Asn-Leu-NH2 (1317.78 Da). The suggested sequences were confirmed by MS analysis of peptide fragments obtained by enzymatic digestion. The peptide PMM1 is a lysyl-arginyl-Thr(6)-bradykinine that belongs to the wasp kinins group. The sequence of the PMM2 peptide is unique; it resembles somewhat the tetradecapeptide amides of the mastoparan group; however, the chain is extended by three additional amino acid residues. The sequence of PMM3 dodecapeptide is homologous to the peptides of the wasp chemotactic group.

Mass spectrometry strategies for venom mapping and peptide sequencing from crude venoms: case applications with single arthropod specimen

Due to their complexity and diversity, animal venoms represent an extensive source of bioactive compounds such as peptides and proteins. Conventional approaches for their characterization often require large quantities of biological material. Current mass spectrometry (MS) techniques now give access to a wealth of information in a short working time frame with minute amounts of sample. Such MS approaches may now be used for the discovery of novel compounds, and once their structure has been determined they may be synthesized and tested for functional activity. Molecular mass fingerprints of venoms allow the rapid identification of known toxins as well as preliminary structural characterization of new compounds. De novo peptide sequencing by tandem mass spectrometry (MS/MS) offers rapid access to partial or total primary peptide structures. This article, written as a tutorial, also contains new material: molecular mass fingerprint analysis of Orthochirus innesi scorpion venom, and identification of components from bumblebee Bombus lapidarius venom, both collected from one single specimen. The structure of the three major peptides detected in the Bombus venom was fully characterized in one working day by de novo sequencing using an electrospray ionization hybrid quadrupole time-of-flight instrument (ESI-QqTOF) and a matrix-assisted laser desorption ionization time-of-flight instrument (MALDI-LIFT-TOF-TOF). After presenting the MS-based sequence elucidation, perspectives in using MS and MS/MS techniques in toxinology are discussed.

Dominulin A and B: two new antibacterial peptides identified on the cuticle and in the venom of the social paper wasp Polistes dominulus using MALDI-TOF, MALDI-TOF/TOF, and ESI-ion trap

Two new antibacterial peptides, denominated as Dominulin A and B, have been found on the cuticle and in the venom of females of the social paper wasp Polistes dominulus. The amino acidic sequence of the two peptides, determined by mass spectrometry, is INWKKIAE VGGKIL SSL for Dominulin A (MW = 1854 Da) and INWKKIAEIGKQVL SAL (MW = 1909 Da) for Dominulin B. Their presence on the cuticle was confirmed using MALDI-TOF by means of micro-extractions and direct analyses on body parts. The presence in the venom and the primary structure of the dominulins suggest their classification in the mastoparans, a class of peptides found in the venom of other Aculeate hymenoptera. Their antimicrobial action against Gram+ and Gram- bacteria fits in the range of the best natural antimicrobial peptides. Dominulins can represent an important defense of the colony of Polistes dominulus against microbial pathogens.

Novel Biologically Active Peptides from the Venom of Polistes rothneyi iwatai

Four novel peptides, polistes-mastoparan-R1, 2, 3, and polistes-protonectin, were isolated from the venom of a paper wasp, Polistes rothneyi iwatai. MALDI-TOF MS analysis of a small amount of the crude venom gave six molecular-related ion peaks. Among them, m/z 1565 was expected to be a novel peptide. Purification of the crude venom by HPLC gave two known kinins, Thr6-bradykinin and Ala-Arg-Thr6-bradykinin, and four novel peptides named polistes-mastoparan-R1, 2, and 3, and polistes-protonectin. Polistes-mastoparan-R1, 2, and 3 (Pm-R) were tetradecapeptides that possess high sequence homology with that of mastoparan. The sequence of polistes-protonectin was similar to that of protonectin isolated from a Brazilian paper wasp. Histamine-releasing activities of Pm-R1, 2, and 3 were more potent than that of mastoparan. Polistes-protonectin exhibited the most potent hemolytic activity in comparison with the four novel peptides and mastoparan.

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.

Antimicrobial activity of conditioned medium fractions from Spodoptera frugiperda Sf9 and Trichoplusia ni Hi5 insect cells

Concentrated conditioned medium (CM) fractions from Spodoptera frugiperda Sf9 and Trichoplusia ni cells, eluting from a gel filtration column at around 10 kDa, were found to exhibit strong antibacterial activity against Bacillus megaterium and Escherichia coli. The B. megaterium cells incubated in the CM fraction from Sf9 cells rapidly lost viability: after 8 min the viability had decreased to 0.7%, as compared with the control. Addition of the CM fraction to E. coli cells resulted in a less drastic drop in viability: 65% viability was lost after 60 min of incubation. Further, exposure to the CM fraction caused a substantial leakage of intracellular proteins, as demonstrated by SDS-PAGE analysis. Cell lysis was confirmed by optical density measurements, microscopic investigations and flow cytometry. B. megaterium exposed to a CM fraction from T. ni cells lost 97% of their viability in about 40 min. Ubiquitin, thioredoxin and cyclophilin were identified in the antibacterial fraction from Sf9 cells by mass spectrometry and N-terminal amino acid sequencing. Other proteins in the fraction gave no matches in a database search. Since ubiquitin was shown not to cause the antimicrobial effect and thioredoxin and cyclophilin were likely not involved, the responsible agent may be an unknown protein, not yet registered in databases. The antimicrobial effect of the CM fraction from T. ni cells most probably comes from a lysozyme precursor protein.

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.