How bradykinin alters the lipid membrane structure: A spin label comparative study with bradykinin fragments and other cations

• Published in: BIOPOLYM Vol. 54; no. 3; pp. 211 - 221
• Main Authors: Turchiello, R. F., Juliano, L., Ito, A. S., Lamy-Freund, M. T.
• Format: Journal Article
• Language: English
• Published: New York John Wiley & Sons, Inc 01.09.2000
• Subjects: Amino Acid Sequence; Biological membranes; bradykinin; Bradykinin - chemistry; Bradykinin - pharmacology; bradykinin fragments; Cations - pharmacology; dimyristoyl phosphatidylglycerol vesicle; Electron Spin Resonance Spectroscopy; Fluidity; Gels; In Vitro Techniques; Lipid Bilayers - chemistry; Lipids; Membrane Lipids - chemistry; Molecular structure; Peptide Fragments - chemistry; Peptide Fragments - pharmacology; peptide-lipid interaction; Phase transitions; Phosphatidylglycerols - chemistry; Polymeric membranes; Polypeptides; spin label; Spin Labels; Thermal effects
• ISSN: 0006-3525; 1097-0282
• DOI: 10.1002/1097-0282(200009)54:3<211::AID-BIP70>3.0.CO;2-P

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‐Arg9–BK, des‐Arg1–BK, and Arg–Pro–Pro–Gly–Phe or BK1–5), with anionic vesicles of dimyristoyl phosphatidylglycerol (DMPG). For temperatures above the lipid gel–liquid crystal thermal transition (Tm ≈ 20°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 < Tm), BK was found to display a much stronger interaction with the membrane, decreasing the bilayer fluidity. At temperatures around 15°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°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‐Arg9–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 Zn2+, and the peptide pentalysine. The data presented here are discussed in the light of the different BK and BK fragments biological activities. © 2000 John Wiley & Sons, Inc. Biopoly 54: 211–221, 2000