The Study of Lipid-Protein Interactions: Effect of Melittin on Phase Transition of Phosphatidylethanolamine and Sensitivity of Phospholipases to Phase State

The effects of melittin on the bilayer-to-inverted hexagonal (H11) phase transition of egg phosphatidylethanolamine (EPE) and the influence of the phase state of membrane matrix on hydrolysis of EPE by phospholipases have been studied. The phase transitions were measured using the fluorescent probe...

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Bibliographic Details
Published in:Journal of biochemistry (Tokyo) 1991-11, Vol.110 (5), p.732-735
Main Authors: Nishiya, Takako, Chou, Hui Li
Format: Article
Language:English
Subjects:
Enzyme Stability - drug effects
Hydrolysis
Kinetics
Lipid Bilayers - antagonists & inhibitors
Melitten - pharmacology
Phosphatidylethanolamines - chemistry
Phosphatidylethanolamines - pharmacology
Phospholipases - chemistry
Phospholipases - drug effects
Spectrometry, Fluorescence
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Summary:The effects of melittin on the bilayer-to-inverted hexagonal (H11) phase transition of egg phosphatidylethanolamine (EPE) and the influence of the phase state of membrane matrix on hydrolysis of EPE by phospholipases have been studied. The phase transitions were measured using the fluorescent probe N-(7-nitro-2,l,3-benzoxadiazol-4-yl)phosphatidyl-ethanolamine (N-NBD-PE) and differential manning calorimetry. In the presence of melittin at a lipid-to-melittin molar ratio (R1) of 200,100,and 20, the phase transition of EPE disappeared, indicating that melittin stabilizes the bilayer structure. In the presence of 10 mol% of cholesterol, the phase transition temperature (TH) decreased and TH was observed even in the presence of melittin at R1 of 200 and 100. The fluorescence intensity of the tryptophan residue of melittin is sensitive to the phase transition and the wavelength of emission maxima shift from 352 to337 nm upon addition of EPE and EPE-cholesterol (10 mol%) at R1 of 200. Kinetic parameters for phospholipase-catalyzed hydrolysis of EPE in bilayer and H11 phases showed that H11 phase of EPE is a poorer substrate for phospholipases and that cholesterol decreases the susceptibility of EPE to phospholipases.
ISSN:0021-924X
DOI:10.1093/oxfordjournals.jbchem.a123649