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      The effects of the C-terminal amidation of mastoparans on their biological actions and interactions with membrane-mimetic systems.

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          Polycationic peptides may present their C-termini in either amidated or acidic form; however, the effects of these conformations on the mechanisms of interaction with the membranes in general were not properly investigated up to now. Protonectarina-MP mastoparan with an either amidated or acidic C-terminus was utilized to study their interactions with anionic and zwitterionic vesicles, using measurements of dye leakage and a combination of H/D exchange and mass spectrometry to monitor peptide-membrane interactions. Mast cell degranulation, hemolysis and antibiosis assays were also performed using these peptides, and the results were correlated with the structural properties of the peptides. The C-terminal amidation promotes the stabilization of the secondary structure of the peptide, with a relatively high content of helical conformations, permitting a deeper interaction with the phospholipid constituents of animal and bacterial cell membranes. The results suggested that at low concentrations Protonectarina-MP interacts with the membranes in a way that both terminal regions remain positioned outside the external surface of the membrane, while the α-carbon backbone becomes partially embedded in the membrane core and changing constantly the conformation, and causing membrane destabilization. The amidation of the C-terminal residue appears to be responsible for the stabilization of the peptide conformation in a secondary structure that is richer in α-helix content than its acidic congener. The helical, amphipathic conformation, in turn, allows a deeper peptide-membrane interaction, favoring both biological activities that depend on peptide structure recognition by the GPCRs (such as exocytosis) and those activities dependent on membrane perturbation (such as hemolysis and antibiosis).

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          Author and article information

          Biochim. Biophys. Acta
          Biochimica et biophysica acta
          Elsevier BV
          Oct 2014
          : 1838
          : 10
          [1 ] Institute of Biosciences of Rio Claro, Universidade Estadual Paulista (UNESP), C.E.I.S./Department of Biology, Rio Claro, SP, Brazil.
          [2 ] IBILCE - Universidade Estadual Paulista (UNESP), Department of Chemistry and Environmental Sciences, São José do Rio Preto, SP, Brazil.
          [3 ] IBILCE - Universidade Estadual Paulista (UNESP), Campus of São José do Rio Preto, Department of Physics, São José do Rio Preto, SP, Brazil.
          [4 ] CEBio, Núcleo de Saúde (NUSAU), Universidade Federal de Rondônia (UNIR), Porto Velho, RO, Brazil.
          [5 ] Institute of Biosciences of Rio Claro, Universidade Estadual Paulista (UNESP), C.E.I.S./Department of Biology, Rio Claro, SP, Brazil. Electronic address: mspalma@rc.unesp.br.


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