Cytochrome P450 17A1 (CYP17) is a haem-containing, membrane bound enzyme situated at a key branch of steroidogenic pathways. CYP17 is a dual function enzyme that catalyses 17α-hydroxylation of progestogens to mineralo- or glucocorticoid precursors and 17,20-lyase reactions of 17α-hydroxylates to androgen precursors. Pharmacological inhibition of CYP17-mediated androgen-precursor synthesis is used in the treatment of advanced prostate cancer. However, current therapeutics bind to the CYP17 active-site and lack selectivity towards the lyase reaction, resulting in further complications from a lack of corticoids.
We aim to improve treatment of prostate cancer through the development of a selective CYP17 lyase inhibitor. The initial step towards this goal, is to employ molecular dynamic simulations to investigate the positive-allosteric modulation of CYP17’s lyase activity by cytochrome b5 (cyt b5) and to explore specific point mutations that can selectively inhibit the lyase reaction. Within a membrane environment, the dynamics of full-length models of CYP17, and V366M and E305G mutants were simulated in the absence of substrate, or with a hydroxylase substrate (pregnenolone) or a lyase substrate (17α-OH pregnenolone). In addition, the effects of protein-protein interaction of cyt b5 with CYP17 were examined. Analysis of the trajectories using a combination of root mean square-deviations and fluctuations, as well as key interaction distances and angles has so far provided insights into the allosteric coupling between the cyt b5 interface and the haem-substrate interaction. Monitoring cavities and pockets throughout the trajectories has revealed the most likely druggable sites. In general, cyt b5 was seen to decrease movement and flexibility within the CYP17 enzyme, however some regions, not necessarily obvious for haem-substrate rearrangement were also seen to be altered. Using the data, we aim to define a dynophore for screening of molecular databases for candidate selective CYP17 lyase inhibitors.