Orientation of cytochrome P450scc in Langmuir-Blodgett monolayers

Monolayers of cytochrome P450scc and its complex with adrenodoxin were formed by Langmuir techniques and covalently immobilized on the solid substrates. The orientation of hemeprotein molecules was studied using polyclonal antibodies specific to the intact cytochrome P450scc molecule and its tryptic fragments F1 and F2, representing N- and C-terminal parts of the hemeprotein molecule. Specific interactions of the Langmuir films of cytochrome P450scc with adrenodoxin were investigated, and the position of the ferredoxin binding site at the hemeprotein molecule was identified. It was shown that the molecular orientation of the P450scc-AD (adrenodoxin) complex at the water-air interface is dependent on the surface density of the monolayer. The P450scc molecules do not denature upon spreading on the water surface. The formed monolayer can be transferred from the air-water interface to the surface modified with siloxane polymer and covalently immobilized without damage to the structure. A model considering the mode of orientation of cytochrome P450scc molecules on the air-water interface in dependence on the surface pressure is discussed.