The stabilizing effect of BSA on the rat ovarian LH/hCG receptor was analyzed by thermal
perturbation technique. Thermal destabilization of the receptor with arachidonic acid
along with digestion of membrane with phospholipase A2 and reversal of these effects when BSA was used as fatty acids scavenger, may indicate
that free fatty acids are responsible for instability of the LH/hCG receptor. This
destabilizing effect may be caused by the presence of a net negative surface charge
provided by fatty acids. This presumption was corroborated by the reconstitution of
delipidated LH/hCG receptor into proteoliposomes. Delipidated receptor lost to a great
extent its binding activity and thermal stability. The receptor was fully reactivated
by the reconstitution into proteoliposomes with neutral phosphatidylcholine but not
with negatively charged phosphatidylserine and phosphatidylglycerol. Thermal inactivation
of the LH/hCG receptor by delipidation was entirely inverted by treatment with phosphatidylcholine
but the presence of negatively charged phospholipids did not change the heat inactivation
profile of hCG-binding sites.
LH/hCG receptor - Thermal inactivation - Fatty acids - Proteoliposomes - Phospholipids
