Molecular mechanisms of interactions between phospholipids and liver microsomal cytochrome P-450 LM2.

The interactions between cytochrome P-450 LM2, NADPH-dependent P-450 reductase and different phospholipids have been analysed in reconstituted systems utilizing spin equilibrium and the reduction reaction as sensitive probes. The results have been correlated with structural data derived from second derivative spectroscopic measurements. The data obtained indicate that phospholipids with acidic groups are of special importance in shifting the spin equilibrium to the high spin state. The detergent substitution of phospholipids, on the other hand, in the reduction reaction provides evidence that the capability to shift the spin state is not strictly correlated with the functional integrity of the system. The results imply that the phospholipids exert a linker function orienting the proteins within the bilayer into a proper interaction state. This function can be substituted by detergents. The phospholipid effect is specified by their head groups and increases with negative charges.