title: How bradykinin alters the lipid membrane structure: a spin label comparative study with bradykinin fragments and other cations.
abstract: Electron spin resonance spectroscopy of several different spin labels was used to comparatively study the interaction of the cationic peptide hormone bradykinin (BK; Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg), and some BK fragments (des-Arg(9)-BK, des-Arg(1)-BK, and Arg-Pro-Pro-Gly-Phe or BK(1-5)), with anionic vesicles of dimyristoyl phosphatidylglycerol (DMPG). For temperatures above the lipid gel-liquid crystal thermal transition (T(m) approximately 20 degrees C), membrane-incorporated spin labels indicated that all peptides (total concentration of 10 mol % relative to lipid) interact with the bilayer, turning the membrane less fluid, both at its surface and center, suggesting a partial penetration of the peptides into the membrane core. However, in the lipid gel phase (t < T(m)), BK was found to display a much stronger interaction with the membrane, decreasing the bilayer fluidity. At temperatures around 15 degrees C the BK-DMPG system was found to present a hysteresis, evinced by the different electron spin resonance spectra yielded upon cooling and heating the sample. System reversibility was found at all other temperatures (0-45 degrees C). That effect could not be assigned to the BK higher concentration at the membrane surface, due to its higher net charge (2(+)) compared to the fragments (1(+)), because ten times more des-Arg(9)-BK (100 mol %) yielded opposite result. Further, that was found to be a result rather different from those elicited by the other cations tested: the monovalent Na(+), the divalent Zn(2+), and the peptide pentalysine. The data presented here are discussed in the light of the different BK and BK fragments biological activities.
authors.affiliation: Instituto de Física, Universidade de S. Paulo, CP 66318, CEP 05315-970, S. Paulo, SP, Brazil.
authors.forename: R F
authors.initials: RF
authors.lastname: Turchiello
authors.forename: L
authors.initials: L
authors.lastname: Juliano
authors.forename: A S
authors.initials: AS
authors.lastname: Ito
authors.forename: M T
authors.initials: MT
authors.lastname: Lamy-Freund
mesh_terms: D000595:Amino Acid Sequence; D001920:Bradykinin / Q000737:chemistry* / Q000494:pharmacology; D002412:Cations / Q000494:pharmacology; D004578:Electron Spin Resonance Spectroscopy; D066298:In Vitro Techniques; D008051:Lipid Bilayers / Q000737:chemistry; D008563:Membrane Lipids / Q000737:chemistry*; D010446:Peptide Fragments / Q000737:chemistry* / Q000494:pharmacology; D010715:Phosphatidylglycerols / Q000737:chemistry; D013113:Spin Labels
chemical_list: D002412:Cations; D008051:Lipid Bilayers; D008563:Membrane Lipids; D010446:Peptide Fragments; D010715:Phosphatidylglycerols; D013113:Spin Labels; C002773:dimyristoylphosphatidylglycerol; D001920:Bradykinin