Distinct Conformations of Mirabegron Determined by MicroED - PubMed (original) (raw)

Distinct Conformations of Mirabegron Determined by MicroED

Jieye Lin et al. bioRxiv. 2023.

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Abstract

Mirabegron, commonly known as "Myrbetriq", has been widely prescribed as a medicine for overactive bladder syndrome for over a decade. However, the structure of the drug and what conformational changes it may undergo upon binding its receptor remain unknown. In this study, we employed microcrystal electron diffraction (MicroED) to reveal its elusive three-dimensional (3D) structure. We find that the drug adopts two distinct conformational states (conformers) within the asymmetric unit. Analysis of hydrogen bonding and packing demonstrated that the hydrophilic groups were embedded within the crystal lattice, resulting in a hydrophobic surface and low water solubility. Structural comparison revealed the presence of _trans_- and _cis_- forms in conformers 1 and 2, respectively. Comparison of the structures of Mirabegron alone with that of the drug bound to its receptor,1 the beta 3 adrenergic receptor (β3AR) suggests that the drug undergoes major conformational change to fit in the receptor agonist binding site. This research highlights the efficacy of MicroED in determining the unknown and polymorphic structures of active pharmaceutical ingredients (APIs) directly from powders.

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Figures

Figure 1.

Figure 1.

MicroED structures of Mirabegron: (A) Chemical structure; (B) MicroED structure of Mirabegron at 1 Å resolution. The 2Fo-Fc map is shown in blue; (C) Conformers 1 and 2 (_trans_- and _cis_-, respectively) observed in the unit cell; MicroED structure of Mirabegron was solved by SHELXT and refined using SHELXL. (D) Overlay of the two conformers.

Figure 2

Figure 2

Hydrogen-bond interactions in Mirabegron crystal packing. The hydrogen-bond interactions are represented by the dashed lines. The contact atoms are labeled.

Figure 3

Figure 3

Overlay of MicroED and Cryo-EM structures of Mirabegron inside of the dog β3AR (PDB entry: 7DH5). (A) Overall view; (B) Overlay of conformer 1 and 2 (MicroED) and Cryo-EM structure; (C) View of the Mirabegron binding pocket viewed from the extracellular side of the membrane. Conformer 1 was colored in blue, conformer 2 was colored in red, Cryo-EM ligand structure was colored in grey, β3AR was colored in white surface. H atoms were omitted for clarity. This analysis shows that Mirabegron undergoes a large conformational change upon binding to the receptor as the structures of the drug alone (conformers 1 and 2) cannot fit otherwise.

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