SPR Analysis of Adrenodoxin Interaction with CYP11B1 Embedded into the Lipid Bilayer

Surface plasmon resonance (SPR) is a relevant method for studying interactions involving membrane proteins, mitochondrial proteins in particular. Currently, there is only a little information on the interaction of mitochondrial proteins with their partners, such as electron carriers, in lipid microenvironment. In this work, using cytochrome P450 11β-hydroxylase (CYP11B1) and adrenodoxin (Adx) as an example, we showed that SPR analysis can be used for studying protein–protein interactions in lipid microenvironment. Kinetic and equilibrium parameters of the CYP11B1-Adx complexes in lipid bilayers of different compositions were determined. Our results reveal that the CYP11B1-Adx complex in cardiolipin-containing bilayer demonstrates increased stability: nearly tenfold reduction in the equilibrium dissociation constant (Kd) compared to the bilayer without cardiolipin. The interaction between redox proteins is highly sensitive to the lipid structure. The immobilized protein and the lipid composition should be selected in each case, but overall, the obtained data are highly complementary for studying membrane proteins.