Gramicidin conformational studies with mixed-chain unsaturated phospholipid bilayer systems

Journal Article · Tue Feb 04 00:00:00 EST 1992 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00119a020· OSTI ID:5687834

Cox, K J; Ho, Cojen; Lombardi, J V; Stubbs, C D ^[1]

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1. Thomas Jefferson Univ., Philadelphia, PA (United States)

The transition of gramicidin from a nonchannel to a channel form was investigated using mixed-chain phosphatidylcholine lipid bilayers. Gramicidin and phospholipids were codispersed, after removal of the solvents chloroform/methanol or trifluoroethanol which resulted in nonchannel and channel conformations, respectively, as confirmed using circular dichroism (CD). The fluorescence emission maxima of the nonchannel form were shifted toward shorter wavelengths by heating at 60C (for 0-12 h), which converted it to a channel form, again as confirmed by CD. The channel form did not respond to heat treatment. Heat treatment also increased the fluorescence anisotropy of the nonchannel gramicidin tryptophans. The rate of transition from the nonchannel to channel conformation was found to be faster is phosphatidylethanolamine was present in combination with phosphatidylcholine compared to phosphatidylcholine alone. Using the fluorescence anisotropy of the membrane lipid probe, 1,6-diphenyl-1,3,5-hexatriene, it was also shown that the motional properties of the surrounding lipid acyl chains differed for the channel and nonchannel gramicidin conformations. The possibility that lipids tending to favor the hexagonal phase (H{sub II}) would enhance the rate of the nonchannel to channel transition was supported by {sup 31}P NMR which revealed the presence of some H{sub II} lipids in the channel preparations. The results of this study suggest that gramicidin may serve as a useful model for similar conformational transitions in other more complex membrane proteins.

• OSTI ID: 5687834
• Journal Information: Biochemistry; (United States), Vol. 31:4; ISSN 0006-2960
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
MEMBRANE PROTEINS
CONFORMATIONAL CHANGES
MEMBRANES
NUCLEAR MAGNETIC RESONANCE
ANISOTROPY
FLUORESCENCE
MAGNETIC CIRCULAR DICHROISM
PHOSPHOLIPIDS
PHOSPHORUS 31
DICHROISM
ESTERS
ISOTOPES
LIGHT NUCLEI
LIPIDS
LUMINESCENCE
MAGNETIC RESONANCE
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANIC PHOSPHORUS COMPOUNDS
PHOSPHORUS ISOTOPES
PROTEINS
RESONANCE
STABLE ISOTOPES
550201* - Biochemistry- Tracer Techniques