The effect of dilauroyl-L-3-phosphatidylcholine on the interaction between cytochrome P-450 1A1 and benzo[a]pyrene.

ABSTRACT

Fluorescence quenching of benzo[a]pyrene (BP) by cytochrome P-450 1A1 was used to probe the effect of the lipid, dilauroyl-L-3-phosphatidylcholine, on this substrate-enzyme interaction. In the presence of lipid, a monoclonal antibody to this P-450 maximally inhibited BP binding at an antibody-to-P-450 ratio of 12, corresponding to an antibody crosslinked P-450 complex. The antibody did not inhibit BP binding in the absence of lipid. These results indicate that when P-450 is subjected to the orientational constraints imposed by antibody-mediated crosslinking, the lipid alters the conformation or quaternary structure of the P-450 oligomer in a manner which changes its affinity for BP.