Analysis of Testosterone Binding with Cytochrome P450 11?-Hydroxylase and Its Variants Through Computational Approach

Abstract

Background: Cytochrome P450 11?-hydroxylase (H11b) converts testosterone (T) into 11-hydroxytestosterone. In Clarias batrachus (catfish), H11b occurs in regular form and has three variants as well. The variant forms contain the complete steroid binding site, though they lack other regions. Thus, they are suggested to be involved in regulating steroid concentration. Method: The structure of H11b and its three variants, Var1, Var2 and Var3 were modeled by homology modeling using human cholesterol side-chain cleavage enzyme, CYP11A1 as a template. The binding of T with the H11b in holo and apo (non-heme state) forms and with all three variants was studied using docking. Furthermore, molecular dynamics simulations of the protein-ligand complexes were carried out and the binding energies of T were calculated using the molecular mechanics-Poisson?Boltzmann surface area (MM-PBSA) method. Results: The analysis showed that the regular protein in its apo-form had the largest binding affinity with T followed by holo-form and Var1. The higher binding affinity was found to be driven by van der Waals interactions. Var3 had the least binding affinity possibly due to the high polar solvation energy. Conclusion: The differences in the binding affinities suggest that the competitive binding of T between H11b and its variants could be the key factor in regulating the synthesis of 11-hydroxytestosterone.

Keywords

• 11?-hydroxylase
• variant forms
• homology modeling
• molecular dynamics simulation
• binding affinity