1UCQ

Crystal structure of the L intermediate of bacteriorhodopsin

1UCQ の概要

• エントリーDOI: 10.2210/pdb1ucq/pdb
• 関連するPDBエントリー: 1iw6 1iw9 1ixf
• 分子名称: bacteriorhodopsin, beta-D-galactopyranose-(1-6)-alpha-D-mannopyranose-(1-2)-alpha-D-glucopyranose, RETINAL, ... (6 entities in total)
• 機能のキーワード: proton pump, retinal protein, membrane protein, protein-lipid complex, reaction intermediate, proton transport
• 由来する生物種: Halobacterium salinarum
• 細胞内の位置: Cell membrane; Multi-pass membrane protein: P02945
• タンパク質・核酸の鎖数: 1
• 化学式量合計: 31912.25

構造登録者

Kouyama, T.,Nishikawa, T.,Tokuhisa, T.,Okumura, H. (登録日: 2003-04-17, 公開日: 2003-12-30, 最終更新日: 2024-10-30)

主引用文献

Kouyama, T.,Nishikawa, T.,Tokuhisa, T.,Okumura, H.
Crystal Structure of the L Intermediate of Bacteriorhodopsin: Evidence for Vertical Translocation of a Water Molecule during the Proton Pumping Cycle.
J.Mol.Biol., 335:531-546, 2004

PubMed Abstract: 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.

PubMed: 14672661
DOI: 10.1016/j.jmb.2003.10.068

実験手法

X-RAY DIFFRACTION (2.4 Å)