Figure 3

Dimer interface and photoexcited state of DsLOV. (A) The dimer of DsLOV (dark state) showing the N-terminus (A´α) mediated dimer interface, based on PISA analysis [33]. The secondary structure elements are colored with helices in light blue; β strands in light green, and loops in yellow. The chromophore riboflavin (RBF) is shown as stick model and is colored by element: carbon, yellow; nitrogen, blue; oxygen, red. The intersubunit hydrogen bonds are shown as broken lines between the residues shown as stick models and colored by element. Specifications on the hydrogen bond distance and the atoms involved are provided in the text. Side chain conformations of R117 and R119 in photoexcited state are shown superimposed in coral. Position of L27 and E32 are indicated by arrowheads. (B) Superposition of dark and photoexcited crystal structures. Side chains of residues shown as stick models are colored by element for dark state as in A, and in coral for photoexcited state. A shift seen in the respective Iβ backbone (dark state- light blue and photoexcited- coral) is highlighted in the oval area. For clarity, rest of the region is shown as ribbon representation in transparent grey. Note the additional H-bond between Q135-NE2 and N5 of RBF molecule in the photoexcited state. The view in this figure is of the monomer (right) of the dimer shown in panel A, which is rotated ~ 180° around the horizontal axis.