Homology Modeling of Lanosterol 14α-Demethylase ofCandida albicansandAspergillus fumigatusand Insights into the Enzyme-Substrate Interactions

Abstract

The crystal structure of 14alpha-sterol demethylase from Mycobacterium tuberculosis (MT_14DM) provides a good template for modeling the three dimensional structure of lanosterol 14alpha-demethylase, which is the target of azole antifungal agents. Homologous 3D models of lanosterol 14alpha-demethylase from Candida albicans (CA_14DM) and Aspergillus fumigatus (AF_14DM) were built on the basis of the crystal coordinates of MT_14DM in complex with 4-phenylimidazole and fluconazole. The reliability of the two models was assessed by Ramachandran plots, Profile-3D analysis, and by analyzing the consistency of the two models with the experimental data on the P450(14DM). The overall structures of the resulting CA_14DM model and AF_14DM model are similar to those of the template structures. The two models remain the core structure characteristic for cytochrome P450s and most of the insertions and deletions expose the molecular surface. The structurally and functionally important residues such as the heme binding residues, the residues lining the substrate access channel, and residues in active site were identified from the model. To explore the binding mode of the substrate with the two models, 24(28)-methylene-24,25-dihydrolanosterol was docked into the active site of the two models and hydrophobic interaction and hydrogen-bonding were found to play an important role in substrate recognition and orientation. These results provided a basis for experiments to probe structure-function relationships in the P450(14DM). Although CA_14DM and AF_14DM shared similar core structural character, the active site of the two models were quite different, thus allowing the rational design of specific inhibitors to the target enzyme and the discovery of novel antifungal agents with broad spectrum.

Synthesis, Molecular Docking Studies, and Antifungal Activity Evaluation of New Benzimidazole-Triazoles as Potential Lanosterol 14α-Demethylase Inhibitors

“…The affinity of azole antifungals to the lanosterol 14a-demethylase is determined not only by the coordination binding of the nitrogen of azole ring to the heme iron in the active side (N-4 of triazole and N-3 of imidazole) but also by the affinity of N-l substituent for the apoprotein part of the enzyme. The remaining part of the azole antifungal fits in the similar way like lanosterol in the hydrophobic groove of lanosterol 14--demethylase [13][14][15][16][17].…”

Three-Dimensional Model of Lanosterol 14α-Demethylase from Cryptococcus neoformans : Active-Site Characterization and Insights into Azole Binding

“…In previous studies, we have constructed 3D models of CYP51 from Candida albicans (CaCYP51) (20,42) and Aspergillus fumigatus (AfCYP51) (42) through homology modeling. The detailed analysis of the docking models of the substrate and azole inhibitors with CaCYP51 leads to a better understanding of the important interactions between CaCYP51 and its inhibitors, which is useful for the discovery of novel antifungal agents (20,42). Based on the results from molecular modeling, successful structure-based optimization of azole antifungal agents was reported by our group (41).…”

Identification of Y118 Amino Acid Residue in Candida albicans Sterol 14.ALPHA.-Demethylase Associated with the Enzyme Activity and Selective Antifungal Activity of Azole Analogues

“…[3][4][5][6][7][8][9] The structural modifications of these novel azoles were aimed at the side chains attached to C3. In the present study, to investigate whether Y118 residue affect interaction of the enzyme with inhibitors, 3 azole derivatives, idiocona- Fig.…”

“…3,[8][9][10] This model predicted a hypothesis that the phenyl group of the C-3 side chain of azole antifungal compounds interacts with the phenol group of Tyr118, a highly conserved residue in CYP51 family, through the formation of p-p face-to-edge interaction (Fig. 1) Our previous publication established a model to predict that the phenyl group of the C-3 side chain of azole antifungal compounds interacts with the phenol group of Tyr118 through the formation of p p-p p face-to-edge interaction.…”

“…3,[8][9][10] This model predicted a hypothesis that the phenyl group of the C-3 side chain of azole antifungal compounds interacts with the phenol group of Tyr118, a highly conserved residue in CYP51 family, through the formation of p-p face-to-edge interaction (Fig. 1) Wan-Nian ZHANG,* ,a and Cheng HE reliability of the derived pharmacophore model, a series of novel azole compounds on the basis of this model were synthesized and tested for their in vitro antifungal activities in our laboratory.…”