TABLE 5

Binding affinity of different compounds to hPXR and the involvement of amino acid residues

Compounds	PXR Binding Affinity	Hydrophobic Residues	Polar Residues	Charged Residues
Hyperforin	1.03 nM	Leu209A, Met243A, Phe288A	Ser247A, Gln285A	His407A
Rifampicin	1.39 pM	Leu209A, Val211A, Trp299A	Ser247A, Gln285A, Cys284A	His407A
Paclitaxel	20.7 pM	Leu209A,Phe288A, Trp299A, Glu321A, Met323A, His407A, Leu411A	Gln285A	Arg410A
Erlotinib	3.97 µM	Leu209A, Met323A,	Ser247A, His407A
Ketoconazole	2.6 nM	Ser247A, Phe281A, Gln285A, Trp299A, Met323A, His407A, Leu411A, Phe429A^{^a}	Gln285A
A-792611	26.45 pM	Leu209A, Val211A, Met243A, Phe281A, Trp299A, Tyr306A, Leu308A, Glu321A, His407A, Thr408A, Leu411A, Phe429A^{^a}	Gln285A
Silybin A	0.42 nM	Phe251A, Phe281A, Phe288A, Trp299A, Phe429A^{^a}		Lys277A, His407A
Silybin B	1.81 nM	Phe281A, His407A, Leu411A, Phe429A^{^a}		Lys277A, His407A
Isosilybin A	1.83 nM	Phe281A, Trp299A, His407A, Phe429A^{^a}	Trp299A, Gln285A, His327A, Thr408A
Isosilybin B	0.22 nM	Trp299A, Phe281A, Phe429A^{^a}	Ser247A, Gln285A, Thr408A
Taxifolin	4.59 μM	Phe281A, Leu411A	Leu240A, Thr408A
Silychristin	8.68 nM	Met243A, Phe281A, Phe429A^{^a}	Ser247A, Thr408A
Silydianin	0.65 nM	Met323A	Ser247A, Gln285A, His407A	Arg410A

↵^a The amino acid Phe429A is located in the AF-2 domain of PXR and it is likely that PXR antagonists bind the small binding site near the outer surface of PXR at the AF-2 domain.