Direct reconstitution of bacteriorhodopsin into planar phospholipid bilayers--detergent effect

This paper describes how the structure and concentration level of a detergent used for substitution after bacteriorhodopsin (bR) solubilization affect the reconstitution of the bR into phospholipid planar bilayers. A direct insertion method was used for the bR reconstitution into the bilayers. Two detergents representing the two major types were used: sodium deoxycholate with a cholane-ring structure, and octylglucoside with a linear (or chain) structure. We then characterized the reconstitution for the two detergents by considering the detergent separation profiles and the photocurrent variations upon addition of lanthanum chloride and the protonophore FCCP (carbonylcyanide-p-trifluoromethoxyphenylhydrazone). We found that for successful transmembrane reconstitution of bR the detergent with the cholane-ring structure was preferable to that with the linear structure when the detergent concentration was above its critical micellar concentration. This preference was explained by the ease with which the detergent with the cholane-ring structure was removed from protein compared to that with the linear structure. Finally, we proposed a scheme for the reconstitution of the protein.