The Optical Biosensor Studies on the Role of Hydrophobic Tails of NADPH-Cytochrome P450 Reductase and Cytochromes P450 2B4 and b5 upon Productive Complex Formation within a Monomeric Reconstituted System☆

Abstract The optical biosensor study of interaction between microsomal proteins—NADPH-cytochrome P450 reductase, cytochrome P450 2B4, and cytochrome b5—was carried out in the monomeric reconstituted system in the absence of phospholipids. The formation of individual complexes was kinetically characterized and their association and dissociation rate constants were determined. The association rate constants for the complexes formed were found to be close to the diffusiion limit—(0.5–4) × 10 6 M −1 s −1 —while their dissociation rate constants did not exceed 0.5 s −1 . It was shown that the interprotein electron transfer can occur both through complex formation and due to random collision. The dominant role of hydrophobic membraneous protein fragments in formation of productive electron transfer complexes was demonstrated.