Testosterone complex and non-steroidal ligands of human aromatase

Abstract

Cytochrome P450 aromatase (AROM) catalyzes the biosynthesis of estrogen from androgen. Previously crystal structures of human AROM in complex with the substrate androstenedione, and inhibitors exemestane, as well as the newly designed steroidal compounds, have been reported. Here we report the first crystal structure of testosterone complex of human placental AROM. Testosterone binds at the androgen-specific heme distal pocket. The polar and hydrophobic interactions with the surrounding residues resemble the interactions observed for other ligands. The heme proximal region comprises the intermolecular interface in AROM, and also the putative interaction surface of its redox partner cytochrome P450 reductase. Unreported previously, the proximal region is characterized by a large surface cavity, unlike most known P450's. Using five best X-ray data sets from androstenedione and testosterone complexes of AROM, we now unequivocally show the presence of an unexplained ligand electron density inside the proximal cavity. The density is interpreted as ordered five ethylene glycol units of polyethylene glycols used as a solvent for steroids and also in crystallization. Interestingly, polyethylene glycol exhibits weak inhibition of AROM enzyme activity in a time dependent manner. Besides its critical role in the redox partner coupling and electron transfer process, the proximal cavity possibly serves as the interaction site for other molecules that may have regulatory effects on AROM activity. In addition, the new data also reveal a previously unidentified water channel linking the active site to the lipid interface. The channel could be the predicted passage for water molecules involved in catalysis.

Slow-, Tight-Binding Inhibition of CYP17A1 by Abiraterone Redefines Its Kinetic Selectivity and Dosing Regimen

“…This parallel pose has been comparatively observed for steroidal ligands binding to CYP19A1 (e.g. PDB 3EQM, 5JKW; (Ghosh et al, 2018)).…”

Steroids and TRP Channels: A Close Relationship

“…This pocket shows similitude to the cavity used by testosterone in the aromatase (an enzyme that also binds testosterone to convert it into 17β estradiol) [ 183 ]. Additionally, it has been reported that testosterone binds to the AR through a H-bond with an arginine (R752) [ 184 ], similarly to the H-bond predicted for the interaction with the TRPM8 channel.…”

Mechanistic Insights into the Regio‐ and Stereoselectivities of Testosterone and Dihydrotestosterone Hydroxylation Catalyzed by CYP3A4 and CYP19A1

“…Because DHT is highly similar to TES in both chemical structure and conformation, the initial CYP3A4‐DHT complexes were obtained by superimposing DHT onto each of the top‐ranked TES poses. The initial structure of the CYP19A1‐TES complex was taken from the crystal structure (PDB code: 5JKW) . Similarly, DHT was superimposed to TES to obtain the CYP19A1‐DHT complex.…”

“…The initial structure of the CYP19A1-TES complex was taken from the crystal structure (PDB code:5 JKW). [49] Similarly,D HT was superimposed to TES to obtain the CYP19A1-DHT complex.…”