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Membrane order controls both rhodopsin thermal denaturation kinetics and MetaII formation
Author(s) -
Bennett Michael Paul,
Mitchell Drake C
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a242-a
Subject(s) - rhodopsin , chemistry , denaturation (fissile materials) , kinetics , lipid bilayer , diphenylhexatriene , bilayer , membrane , vesicle , membrane fluidity , biophysics , biochemistry , nuclear chemistry , retinal , physics , quantum mechanics , biology
We investigated the effect of membrane composition on the kinetic stability of rhodopsin with respect to thermal unfolding by reconstituting vesicles consisting of SOPC +/− 30% cholesterol and 80:20 SOPC/SDPC +/− 30% cholesterol at lipid:protein (L:P) ratios of 100:1. The activation energy (Ea) of rhodopsin thermal denaturation was calculated by four independent methods: the dependence of transition temperature on scan rate, the dependence of the denaturation rate constant on temperature, the dependence of heat absorption on temperature, and the transition maximum heat capacity. The effects of lipid composition on bilayer order and rhodopsin function were measured with time‐resolved diphenylhexatriene fluorescence polarization and the MetaI‐MetaII equilibrium (Keq). The addition of cholesterol resulted in a significant increase in Ea, while the addition of SDPC to SOPC lowered Ea. Cholesterol increased membrane order and lowered Keq, while the SDPC containing samples had decreased membrane order and higher Keq. This study demonstrates that both protein conformation and the rate of rhodopsin thermal denaturation are sensitive to membrane order, suggesting a P‐L interaction that modulates rhodopsin function and stability through the control of protein conformational space.