INVESTIGADORES
DUPUY Fernando Gabriel
congresos y reuniones científicas
Título:
Evidences of a cooperative partition of the MccJ25 peptide into membranes
Autor/es:
DUPUY, FERNANDO G.; CHEHÍN, ROSANA; MORERO, ROBERTO.
Lugar:
Montevideo, Uruguay
Reunión:
Congreso; XXXVI Reunión Anual de la Sociedad Argentina de Biofisica; 2007
Institución organizadora:
Sociedad Argentina de Biofisica
Resumen:
Microcin J25 is a 21
aminoacid peptide active against Escherichia coli and Salmonella enteritidis
strains. The structure of MccJ25 was elucidated based on mass spectrometry and
nuclear magnetic resonance showing a distinctive lasso-structure with high hydrophobic
character. Our laboratory provided convincing evidence that RNA polymerase is
the main target for MccJ25 action in E. coli. However, peptide activity against
cellular and model membranes has also been shown. In a previous report, the
interaction of tryptophan containing microcin mutants, MccJ25 I13W and MccJ25
V6W with model membranes was studied by means of fluorescence quenching. In
this work, a quantitative study of the partition of the peptides into membranes
was carried out with fluorescence spectroscopy. When liposomes made of
dipalmitoylphosphatidylcholine are added up to 200:1 phospholipid:peptide
ratio, a blue shift of the tryptophan fluorescence spectrum and a sigmoidal
enhancement of the intensity are observed, suggesting a cooperative partitions
of the peptide into the hydrophobic environment. Both the partition coefficient and the Hill
coefficient were calculated by fitting the data to a modified form of the
general hyperbolic partition equation, that takes account the sigmoidal;
behavior observed, using non-linear least-squares analysis (Sigma Plot). To
obtain molecular insights of the peptide partition into membranes, Fourier
transform infrared spectroscopy was used. The peptide spectrum in aqueous
solution shows two principal shoulders centered at 1645 cm-1 and 1625 cm-1
respectively. The later band is shifted 2 cm-1 to higher wavenumber in the
presence of DPPC liposomes, indicating changes in the structure of the peptides
upon lipid binding that could be driving the cooperativism of the partition.
Significant changes were also observed in the onset of the vas [CH2] and vs
[CH2] wavenumbers. However, any detectable effect on the interfacial region of
the phospholipids could be seen