[Comparative study of original and reconstituted by self-assembly endoplasmic reticulum membranes]

A method for biomembrane reconstitution from microsomal proteins and lipids solubilized by sodium cholate consisting in a removal of the detergent by its dialysis followed by treatment with 10% albumin has been developed. A comparison of the original and reconstituted membranes showed that the phospholipid, protein and enzymatic composition of the latter is similar or only slightly different from that of the original ghosts. The reconstituted membranes contained 1.5 times more cytochrome b5 and an equal amount of cytochrome P-450. No more than 20% of cytochrome P-450 was represented by the inactive form. The inactivation rate of the reduced hemoprotein in the reconstituted membranes was lower than in the ghosts. Both in the reconstituted and original membranes the similarity of solubilization patterns of microsomal electron carries upon trypsin treatment was indicative of identical topography of these proteins. The most effective was the reconstitution of NADH and cumole hydroperoxide-dependent N-demethylase, whereas the p-hydroxylase and O-dealkylase activities of the reactivated P-450 were not retained. Hence, no complete reconstitution of the properties of the microsomal membrane and its redox chain was observed in spite of the effective removal of the detergent, similar localization of microsomal electron carriers in the reconstituted membranes and ghosts and the reconversion of cytochrome P-420 into cytochrome P-450.