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

The optical biosensor study of interaction between microsomal proteins-NADP H-cytochrome P450 reductase, cytochrome P450 2B4, and cytochrome b5- was ca rried out in the monomeric reconstituted system in the absence of phospholi pids. The formation of individual complexes was kinetically characterized a nd their association and dissociation rate constants were determined. The a ssociation rate constants for the complexes formed were found to be close t o the diffusiion limit-(0.5-4) x 10(6) M-1 s(-1)-while their dissociation r ate 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 rando m collision. The dominant role of hydrophobic membraneous protein fragments in formation of productive electron transfer complexes was demonstrated. ( C) 1999 Academic Press.