Structural and Functional Insights into Cytochromes P450 11B1 and 11B2 Interaction with Ligands and Redox Partner Proteins

Abstract

Human steroidogenic cytochrome P450 enzymes 11B1 (CYP11B1) and 11B2 (CYP11B2) generate cortisol and aldosterone, controlling stress/immune responses and blood pressure, respectively. Excessive cortisol production by CYP11B1 results in Cushing's disease, while aldosterone overproduction by CYP11B2 causes hypertension and cardiac disease. Treatment of each disease with drugs inhibiting the respective enzyme is impeded because CYP11B1 and CYP11B2 have 93% identical amino acid sequences and no structures of CYP11B1 are available to identify structural differences that could be exploited clinically. A two‐fold strategy is employed herein to support the development of more selective treatment options for Cushing's and hypertension. First, structural differences between human CYP11B1 and CYP11B2 were identified. The first X‐ray structure of human CYP11B1 was solved, doing so in complex with the non‐selective inhibitor fadrozole. Comparison with a previous CYP11B2 structure also binding fadrozole revealed large differences in inhibitor orientation in the respective active sites. The two CYP11B enzymes bind distinct enantiomers of fadrozole, with CYP11B1 binding (S)‐fadrozole and CYP11B2 binding (R)‐fadrozole. Knowledge of the distinct active site architectures will facilitate structure‐based drug design for the treatment of Cushing's and hypertension. A second strategy explores the concept of selective inhibition of CYP11B enzymes interactions with their redox partner protein adrenodoxin (Adx). Binding assays revealed that adrenodoxin binding on the CYP11B2 surface significantly increases CYP11B2 affinity for its substrate in the distant active site, with much less effect on CYP11B1. Any differences in the protein/protein interaction might be exploited to provide an orthogonal approach for selective inhibition of CYP11B enzymes. A combination of structural and functional studies is thus used to identify similarities and differences in CYP11B interactions with Adx and with ligands to facilitate the design of compounds useful in the treatment of Cushing's disease and hypertension.Support or Funding InformationX‐ray data were collected at the Stanford Synchrotron Radiation Lightsource (SSRL). The SSRL Structural Molecular Biology Program is supported by the US Department of Energy Office of Biological and Environmental Research and by the US National Institutes of Health (NIH), National Center for Research Resources, Biomedical Technology Program and the National Institute of General Medical Sciences. This research was funded by R37 GM 076343 and startup funds from the University of MichiganThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.