Conformational studies of NADPH cytochrome P-450 reductase by circular dichroism: interaction with phospholipids.
Ultraviolet circular dichroism spectrum of purified NADPH cytochrome P-450 reductase was characterized by two negative bands centered at 208 and 222 nm. The approximation of the alpha-helical content from the value of the mean residue ellipticity at 222 nm indicated 28% of alpha-helical structures. Heat inactivation of the enzyme was associated to a drastic change in the secondary structure of the protein. Membrane reconstitution experiments by inclusion of the enzyme into liposomes revealed that the conformation of NADPH cytochrome P-450 reductase was sensitive to its phospholipid environment. Egg lecithin as well as synthetic phosphatidylcholines, at the optimal phospholipid-enzyme molar ratio 200, was able to increase up to 37% the mean residue ellipticity at 222 nm. Addition of phosphatidylserine or phosphatidylethanolamine produced no effect. Non-ionic detergent such as Emulgen 913 weakly enhanced the mean residue ellipticity.
D000818:Animals; D002942:Circular Dichroism; D008862:Microsomes, Liver / Q000201:enzymology; D009251:NADPH-Ferrihemoprotein Reductase / Q000032:analysis*; D010713:Phosphatidylcholines / Q000032:analysis; D010743:Phospholipids / Q000032:analysis*; D011487:Protein Conformation; D011489:Protein Denaturation; D013552:Swine
D010713:Phosphatidylcholines; D010743:Phospholipids; D009251:NADPH-Ferrihemoprotein Reductase