13C-NMR studies of membrane lipid-protein interactions upon protein heat denaturation.

Spinach chloroplast membranes were studied by natural abundance carbon-13 nuclear magnetic resonance (13C-NMR) spectroscopy in their normal state and after heat denaturation of membrane proteins. The membrane proteins were denatured by raising the temperature of the sample to 67 degrees C for 5 minutes [YashRoy, R.C. (1991) J. Biochem. Biophys. Methods 22, 55-59]. Line-broadening of 13C-NMR resonances arising from the 1st (carbonyl), 7th, 9th and 12th carbon atom of fatty-acyl chains with reference to the carbonyl (C-1) group shows increased immobilization of lipid fatty-acyl chains at these locations, obviously caused by changes in interactions between membrane lipids and proteins upon heat denaturation of membrane proteins.