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1.
Amino Acids ; 40(1): 91-100, 2011 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-20195659

RESUMO

Some mastoparan peptides extracted from social wasps display antimicrobial activity and some are hemolytic and cytotoxic. Although the cell specificity of these peptides is complex and poorly understood, it is believed that their net charges and their hydrophobicity contribute to modulate their biological activities. We report a study, using fluorescence and circular dichroism spectroscopies, evaluating the influence of these two parameters on the lytic activities of five mastoparans in zwitterionic and anionic phospholipid vesicles. Four of these peptides, extracted from the venom of the social wasp Polybia paulista, present both acidic and basic residues with net charges ranging from +1 to +3 which were compared to Mastoparan-X with three basic residues and net charge +4. Previous studies revealed that these peptides have moderate-to-strong antibacterial activity against Gram-positive and Gram-negative microorganisms and some of them are hemolytic. Their affinity and lytic activity in zwitterionic vesicles decrease with the net electrical charges and the dose response curves are more cooperative for the less charged peptides. Higher charged peptides display higher affinity and lytic activity in anionic vesicles. The present study shows that the acidic residues play an important role in modulating the peptides' lytic and biological activities and influence differently when the peptide is hydrophobic or when the acidic residue is in a hydrophilic peptide.


Assuntos
Citotoxinas/química , Peptídeos/química , Venenos de Vespas/química , Vespas/química , Sequência de Aminoácidos , Animais , Dicroísmo Circular , Citotoxinas/farmacologia , Interações Hidrofóbicas e Hidrofílicas , Peptídeos e Proteínas de Sinalização Intercelular , Modelos Biológicos , Dados de Sequência Molecular , Peptídeos/farmacologia , Espectrometria de Fluorescência , Relação Estrutura-Atividade , Venenos de Vespas/farmacologia
2.
Arch Biochem Biophys ; 486(1): 1-11, 2009 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-19328184

RESUMO

In the last decade, there has been renewed interest in biologically active peptides in fields like allergy, autoimmune diseases and antibiotic therapy. Mast cell degranulating peptides mimic G-protein receptors, showing different activity levels even among homologous peptides. Another important feature is their ability to interact directly with membrane phospholipids, in a fast and concentration-dependent way. The mechanism of action of peptide HR1 on model membranes was investigated comparatively to other mast cell degranulating peptides (Mastoparan, Eumenitin and Anoplin) to evidence the features that modulate their selectivity. Using vesicle leakage, single-channel recordings and zeta-potential measurements, we demonstrated that HR1 preferentially binds to anionic bilayers, accumulates, folds, and at very low concentrations, is able to insert and create membrane spanning ion-selective pores. We discuss the ion selectivity character of the pores based on the neutralization or screening of the peptides charges by the bilayer head group charges or dipoles.


Assuntos
Degranulação Celular/efeitos dos fármacos , Mastócitos/efeitos dos fármacos , Mastócitos/fisiologia , Peptídeos/farmacologia , Venenos de Vespas/farmacologia , Animais , Peptídeos Catiônicos Antimicrobianos/farmacologia , Fenômenos Biofísicos , Dicroísmo Circular , Técnicas In Vitro , Peptídeos e Proteínas de Sinalização Intercelular , Bicamadas Lipídicas/química , Potenciais da Membrana/efeitos dos fármacos , Membranas Artificiais , Modelos Moleculares , Peptídeos/química , Conformação Proteica/efeitos dos fármacos , Ratos , Ratos Wistar , Venenos de Vespas/química
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