Structural changes in SaBphP1 near the BV chromophore. Important residues are marked. Important salt and hydrogen bonds are shown by dashed lines. (a) Effect of adding the PHY domain. Blue atomic structure, CBD-wt; yellow atomic structure, PCM-wt. The electron density (simulated annealing OMIT mFo − DFc, dark blue, contour level: 2σ) is shown for the chromophore and the Thr289 (red). The red arrow indicates the overall trend of the changes. (b) Effect of the T289H mutation. Blue atomic structure: PCM-wt, yellow atomic structure: PCM-T289H. The electron density (simulated annealing mFo − DFc, light blue, contour level: 2σ) is shown for the chromophore and the His289 (red).