TaB-derivative crystals of MUAE. A stereo representation of a section of the experimental electron-density map is shown after phase extension to 2.8 Å resolution, solvent flattening and threefold NCS averaging calculated from SAD phases (blue mesh, contoured at 1σ) together with the anomalous difference Fourier map of tungsten (orange mesh, contoured at 5σ). The Cα trace of the final model (PDB entry 1z7l
) is shown as ribbon representation (black). The TaB cluster at binding site 1 was found by MR at 3.3 Å resolution and is shown in stick representation.