Deuterium and phosphorus-31 nuclear magnetic resonance study of the interaction of melittin with dimyristoylphosphatidylcholine bilayers and the effects of contaminating phospholipase A/sub 2/
The interaction of bee venom melittin with dimyristoylphosphatidylcholine (DMPC) selectively deuteriated in the choline head group has been studied by deuterium and phosphorus-31 nuclear magnetic resonance (NMR) spectroscopy. The action of residual phospholipase A/sub 2/ in melittin samples resulted in mixtures of DMPC and its hydrolytic products that underwent reversible transitions at temperatures between 30 and 35/sup 0/C from extended bilayers to micellar particles which gave narrow single-line deuterium and phosphorus-31 NMR spectra. Similar transitions were observed in DMPC-myristoyllysophosphatidylcholine (lysoPC)-myristic acid mixtures containing melittin but not in melittin-free mixtures, indicating that melittin is able to stabilize extended bilayers containing DMPC and its hydrolytic products in the liquid-crystalline phase. Melittin, free of phospholipase A/sub 2/ activity, and at 3-5 mol % relative to DMPC, induced reversible transitions between extended bilayers and micellar particles on passing through the liquid-crystalline to gel phase transition temperature of the lipid, effects similar to those observed in melittin-acyl chain deuteriated dipalmitoylphosphatidylcholine (DPPC) mixtures. LysoPC at concentrations of 20 mol % or greater relative to DMPC induced transitions between extended bilayers and micellar particles with characteristics similar to those induced by melittin. It is proposed that these melittin- and lysoPC-induced transitions share similar mechanisms. The effects of melittin on the quadrupole splittings and T/sub 1/ relaxation times of head-group-deuteriated DMPC in the liquid-crystalline phase share features similar to the effects of metal ions on DPPC head groups, indicating that the conformational properties of the choline head group in PC bilayers may be affected by melittin and by metal ions in a similar manner.
- Research Organization:
- Oxford Univ., England
- OSTI ID:
- 5767375
- Journal Information:
- Biochemistry; (United States), Vol. 26:18
- Country of Publication:
- United States
- Language:
- English
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LIPASE
BIOCHEMISTRY
MELLITIC ACID
CONFIGURATION INTERACTION
NUCLEAR MAGNETIC RESONANCE
PHOSPHOLIPIDS
DEUTERIUM COMPOUNDS
MEMBRANES
PHOSPHORUS 31
CARBOXYLESTERASES
CARBOXYLIC ACIDS
CHEMISTRY
ENZYMES
ESTERASES
ESTERS
HYDROGEN COMPOUNDS
HYDROLASES
ISOTOPES
LIGHT NUCLEI
LIPIDS
MAGNETIC RESONANCE
NUCLEI
ODD-EVEN NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC PHOSPHORUS COMPOUNDS
PHOSPHORUS ISOTOPES
RESONANCE
STABLE ISOTOPES
550601* - Medicine- Unsealed Radionuclides in Diagnostics