Conformational change of cytochrome P-450 indicated by the measurement of fluorescence-energy transfer.
The conformation of cytochrome P-450 was studied in relation to the interaction with its substrate by the measurement of fluorescence energy transfer. Cytochrome P-450 I-c and cytochrome P-450 II-d, both obtained from the hepatic microsome of polychlorinated biphenyl-treated rats, were used as P-450 type and P-448 type, respectively, and benzo[a]pyrene and 7-ethoxycoumarin were used as substrate. The distance between the donor and acceptor, which was described by the Förster equation, was calculated on the basis of the fluorescence-energy transfer between the substrate as a donor and the heme of the enzyme as an acceptor. The distance was apparently changed by incorporation of the enzyme into phospholipid or by reduction of the heme, indicating that the treatments changed the conformation of the enzyme. Differences in the conformational change were observed between the two enzymes, and the conformational change of cytochrome P-450 II-d using benzo[a]pyrene as a substrate was different from that using 7-ethoxycoumarin. The results suggest that the substrate-binding sites of the two enzymes differ in position toward the heme, and that there are at least two different substrate sites in cytochrome P-450 II-d, one for benzo[a]pyrene and another for 7-ethoxycoumarin.
Y
Y
Omata
Y
Y
Ueno
K
K
Aibara
D000818:Animals; D001564:Benzo(a)pyrene; D002942:Circular Dichroism; D003374:Coumarins; D003577:Cytochrome P-450 Enzyme System; D004735:Energy Transfer; D007527:Isoenzymes; D008297:Male; D008433:Mathematics; D011487:Protein Conformation; D051381:Rats
D003374:Coumarins; D007527:Isoenzymes; C017299:7-ethoxycoumarin; D001564:Benzo(a)pyrene; D003577:Cytochrome P-450 Enzyme System