Figure 2
Structural differences in ligand recognition between SFX and SR. (a) Chemical structure of the N-carbobenzoxy-L-aspartic acid ligand. The carboxymethyl moiety showing alternate conformations is coloured red. (b, c) Stereo representations of the crystal structure relevant to ligand binding in the liganded oil–SFX form (b) and the liganded SR1 form (c). Atoms in the asymmetric unit are shown with atom-type colouring, apart from those of the alternate conformation, which are coloured cyan; symmetry-related atoms are coloured magenta. Important residues, the ligand ZA and two alternate conformations of the carboxymethyl moiety of ZA are labelled. Ligand–protein hydrogen bonds are indicated as dotted lines. The annealed OMIT maps for the ligand molecule with Fourier coefficients 2mFo − DFc (blue; 0.5σ contour level) and mFo − DFc (orange; 3.σ contour level) are overlaid. (b) and (c) were prepared with Discovery Studio (Accelrys). |