Premium
A role for phospholipid polyunsaturation in modulating membrane protein function
Author(s) -
Litman Burton J.,
Mitchell Drake C.
Publication year - 1996
Publication title -
lipids
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.601
H-Index - 120
eISSN - 1558-9307
pISSN - 0024-4201
DOI - 10.1007/bf02637075
Subject(s) - phospholipid , degree of unsaturation , chemistry , vesicle , membrane , rhodopsin , bilayer , lipid bilayer , biophysics , membrane biology , biochemistry , chromatography , biology , retinal
Visual transduction is one of the best characterized G protein—coupled signalling systems. In addition, about 50% of the disk membrane phospholipid acyl chains are 22:6n‐3, making this system ideal for determining the role of polyunsaturation in modulating membrane‐signalling systems. The extent of formation of metarhodopsin II (MII), the G protein—activating photointermediate of rhodopsin, was studied in phospholipid vesicles composed of a variety of phosphatidylcholines, differing in their acyl chain composition at the sn ‐2 position. The amount of MII formed increased progressively with the level of acyl chain unsaturation at the sn ‐2 position. The effect of added cholesterol was to reduce the amount of MII formed. The acyl chain packing free volume of the rhodopsin containing lipid vesicles was characterized by a fractional volume parameter f v derived from measurements of the time‐resolved fluorescence anisotropy decay of the hydrophobic membrane probe 1,6‐diphenyl‐1,3,5‐hexatriene. The relationship among sn ‐2 acyl chain unsaturation, cholesterol content, and MII formation is explained on the basis of variation in f v with bilayer lipid composition and a novel model for the packing of phospholipids containing polyenoic acyl chains, such as 22:6n‐3.