Benzoate X receptor

Moore, L.B., J.M. Maglich, D.D. McKee, B. Wisely, T.M. Willson, S.A. Kliewer, M.H. Lambert and J.T. Moore. Pregnane X receptor (PXR), constitutive androstane receptor (CAR), and benzoate X receptor (BXR) define three pharmacologically distinct classes of nuclear receptors. Mol. Endocrinol. 16 977-986, 2002. 

Amongst the putative anionic guests studied, receptor 1 was found to bind benzoate most strongly with a stability constant of 2.5 x 103 M"1 whilst compound 2 bound dihydrogen phosphate most strongly in DMS0-c/7H20 0.5% (used for solubility reasons) with a stability constant of 1.5 x 103 M"1. 

Figure 5. The X-ray crystal structure of the benzoate complex of receptor 1 (tetrabutylammonium counter cation and non-acidic hydrogen atoms have been omitted for clarity).

Modification of the core motif allows for 2,5-diamido-pyrrole derivatives, 99, having a additional NH hydrogen-bond donor compared with isophthalamide receptors. A binding constant of 2500 M for benzoate in acetonitrile is observed with an asymmetric binding mode apparent in the molecular structure measured by X-ray crystallography. 

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