Figure 2
From: X-ray Crystallographic Structure and Oligomerization of Gloeobacter Rhodopsin
Structural details of GR. (a) Overall structure of GR shown in cartoon representation viewed parallel to the membrane (left), from intracellular side (right, top) and from extracellular side (right, bottom). GR consists of seven transmembrane helices (TM A to TM G, shown in brown) connected by interhelical loops (shown in white) on both sides of the membrane. The β-strands in the B-C loop are shown in green. All-trans-retinal, depicted by stick models, is covalently linked to Lys257 via a protonated Schiff base (shown in yellow). (b) Superimposed structures of GR (brown) and H. salinarum BR (white, PDB entry 1C3W), and GR and XR (white, PDB entry 3DDL), respectively. (c) 3-omega motif of GR formed by π-stacking interactions of the side chains of aromatic residues in TM A (F38), TM B (W95) and B–C loop (Y106). (d) Extracellular side of superimposed GR (brown) and XR (white) structures with the XR-bound SX molecule (cyan). The helix displacements are indicated by red arrows. (e) Potential carotenoid binding site in GR. Salinixanthin (SX) from the crystal structure of XR is superimposed onto the structure of GR. The magnified views compare the location of SX and the retinal in GR (top) and XR (bottom).
