Figure 5 - full size


Figure 5.
Celecoxib binding to ovCOX-1 as determined by x-ray crystallography. (A) A stereoview of celecoxib (yellow) in the active site of COX-1 in the celecoxib/ovCOX-1 structure shown with omit F[o]-F[c] difference density contoured at 2.8σ (gray). Residues in the active site are displayed in green, whereas celecoxib is in yellow. Residues Arg120, Tyr355, and Glu524 lie at the mouth of the COX active site, whereas the catalytic Tyr385 hydrogen bonded to Tyr348 are located at the apex of the hydrophobic channel. (B) Stereoview of celecoxib/ovCOX-1 structure with the opening from the membrane binding domain into the COX active site oriented along plane of the page. Comparison of celecoxib/ovCOX-1 complex (green) and the reference model (1Q4G) (superimposed yellow ribbon and yellow side chains) shows that Ile523, homologous to Val523 in COX-2, adopts an extended rotamer conformation allowing access to the otherwise inaccessible hydrophobic side pocket comprised of residues Leu352, Ser353, Ile517, and Phe518 (some side chains are omitted for clarity). The residues His513 and Gln192 contribute to the outer shell of the side pocket and are included in the figure. Rendering of celecoxib atoms as spheres highlight the steric clash of Ile523 (yellow sticks in bottom panel) with the reference model. In Fig. S6 the positions of the α-carbons of residues 510–520 in the celecoxib/ovCOX-1 and the AA/ovCOX-1 (1DIY) structures relative to the reference model (1Q4G) are compared. (C) Stereoview of two alternate conformations of residues 121–129 in monomer B at the dimer interface traced into the electron density. Monomer A (orange) is shown with celecoxib bound (yellow) and monomer B is shown in the two conformations representing the conformation in the absence of bound inhibitor (blue) and the shift induced by binding of celecoxib (magenta). The side chains of Ser126 and Pro127 are shown in the two conformations and represented as inhibitor bound (+) and unbound (-) next to Glu543 (E543) of the partner monomer also in an alternate conformation. The position of celecoxib in monomer A (yellow sticks) and active site residues Arg120, Glu524, Tyr355, Ser530, and Tyr385 are shown for spatial orientation. Celecoxib in monomer B, which was refined to 50% occupancy in the final model, has been removed to represent the unbound monomer. (D) Enlarged view of the boxed area at the dimer interface shown in C.