1ucq

Crystal structure of the L intermediate of bacteriorhodopsin

spinqualitylabelsall models 1ucq, resolution 2.40Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 1ucq is a 1 chain structure with sequence from Halobacterium salinarum. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: GAL, GLC, L2P, L3P, MAN, RET Related: 1iw6, 1iw9, 1ixf Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function [BACR_HALSA] Light-driven proton pump. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMed For structural investigation of the L intermediate of bacteriorhodopsin, a 3D crystal belonging to the space group P622 was illuminated with green light at 160 K and subsequently with red light at 100 K. This yielded a approximately 1:4 mixture of the L intermediate and the ground-state. Diffraction data from such crystals were collected using a low flux of X-rays ( approximately 2 x 10(15) photons/mm2 per crystal), and their merged data were compared with those from unphotolyzed crystals. These structural data, together with our previous data, indicate that the retinal chromophore, which is largely twisted in the K-intermediate, takes a more planar 13-cis, 15-anti configuration in the L intermediate. This configurational change, which is accompanied by re-orientation of the Schiff base N-H bond towards the intracellular side, is coupled with a large rotation of the side-chain of an amino acid residue (Leu93) making contact with the C13 methyl group of retinal. Following these motions, a water molecule, at first hydrogen-bonded to the Schiff base and Asp85, is dragged to a space that is originally occupied by Leu93. Diffraction data from a crystal containing the M intermediate showed that this water molecule moves further towards the intracellular side in the L-to-M transition. It is very likely that detachment of this water molecule from the protonated Schiff base causes a significant decrease in the pKa of the Schiff base, thereby facilitating the proton transfer to Asp85. On the basis of these observations, we argue that the vertical movement of a water molecule in the K-to-L transition is a key event determining the directionality of proton translocation in the protein. Crystal structure of the L intermediate of bacteriorhodopsin: evidence for vertical translocation of a water molecule during the proton pumping cycle.,Kouyama T, Nishikawa T, Tokuhisa T, Okumura H J Mol Biol. 2004 Jan 9;335(2):531-46. PMID:14672661 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Bacteriorhodopsin 3D structures

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