PMC

3-D overlay of the binding pockets of wild-type CRALBP and α-TTP. Ribbon diagrams of CRALBP (salmon) and of α-TTP (gray) are shown with a numbering scheme according to the CRALBP secondary structure. 11-cis-retinal (salmon) and RRR-α-tocopherol (gray) are depicted as sticks; oxygen atoms are shown in red.

Time courses of the photoisomerization of 11-cis-retinal in the presence of ethanol, wild-type CRALBP, and R234W. The amount present at t = 0 is a_0; the amount present after illumination is a. For a first-order decay process, a = a₀e^−kt. The first-order rate constants calculated from this experiment are k_ethanol = 0.859 × 10⁻³ s⁻¹; k_CRALBP = 0.197 × 10⁻³ s⁻¹; k_R234W = 0.035 × 10⁻³ s⁻¹.

Missense mutations in CRALBP associated with retinitis pigmentosa. The side chains of residues mutated in retinitis pigmentosa are shown as green sticks on a worm model of the protein backbone; the interacting amino acid residues are shown in gray. The 11-cis-retinal ligand is shown as an orange stick, and the cavity surface is shown in orange. Dashed black lines indicate hydrogen bonds; distances are given in Å.

Monomeric structure of CRALBP. (A) Ribbon diagram of wild-type CRALBP bound to 11-cis-retinal. The helices of the N-terminal domain are indicated in green; C-terminal helices are indicated in blue; the helical gate (helices α11 and α12) is indicated in gray; β-strands are indicated in red. The position of R234 is indicated as a yellow sphere, the 11-cis-retinal ligand is shown as orange sticks, and the cavity surface is shown in orange. The cavity surface was calculated with VOIDOO (). (B) View after rotation of A by 90° on the vertical axis. Images were generated with PYMOL ().

Comparison of wild-type and R234W CRALBP. (A) Stereoview of the critically charged cleft of CRALBP superimposed on R234W. Tartrate and interacting residues of the CRALBP basic cleft are depicted as gray sticks. Dashed black lines indicate possible hydrogen bonds and short contacts; distances are given in Å. Corresponding residues of the R234W basic cleft are depicted as salmon sticks. (B) Stereoview of the domino-like structural transition in CRALBP by the R234W mutation. Side chains of wild-type CRALBP (gray) that participate in a cascade of side-chain flips in R234W (salmon) are depicted as sticks, the protein backbones are shown as a worm model. The cavity surface of the wild-type CRALBP and the 11-cis-retinal chromophore are shown in orange.

Ligand binding pocket of CRALBP. (A) Cavity-overlay of wild-type CRALBP (gray) onto R234W (orange). The corresponding 11-cis-retinal ligands are shown as gray and orange sticks, respectively. (B) Close-up view of the ligand-binding pocket of R234W. Side chains (gray) that form van der Waals contacts with 11-cis-retinal (orange) or participate in hydrogen bonding in the ligand binding pocket are shown. The protein backbone is shown as a worm model. The electron density of the ligand is shown as a mesh at 1 σ in the 2F_o–F_c map. Dashed black lines indicate hydrogen bonds; distances are given in Å.