1F4Z

BACTERIORHODOPSIN-M PHOTOINTERMEDIATE STATE OF THE E204Q MUTANT AT 1.8 ANGSTROM RESOLUTION

Summary for 1F4Z

• Entry DOI: 10.2210/pdb1f4z/pdb
• Related: 1C3W 1C8R 1C8S 1f50
• Descriptor: BACTERIORHODOPSIN, 1-[2,6,10.14-TETRAMETHYL-HEXADECAN-16-YL]-2-[2,10,14-TRIMETHYLHEXADECAN-16-YL]GLYCEROL, 2,10,23-TRIMETHYL-TETRACOSANE, ... (5 entities in total)
• Functional Keywords: ion pump, membrane protein, retinal protein, lipids, photoreceptor, haloarchaea, 7-transmembrane, ion transport, merohedral twinning, e204q mutant m state, photocycle intermediate, proton transport
• Biological source: Halobacterium salinarum
• Cellular location: Cell membrane; Multi-pass membrane protein: P02945
• Total number of polymer chains: 1
• Total formula weight: 33834.30

Authors

Luecke, H.,Schobert, B.,Cartailler, J.P.,Richter, H.T.,Rosengarth, A.,Needleman, R.,Lanyi, J.K. (deposition date: 2000-06-10, release date: 2000-08-09, Last modification date: 2024-11-13)

Primary citation

Luecke, H.,Schobert, B.,Cartailler, J.P.,Richter, H.T.,Rosengarth, A.,Needleman, R.,Lanyi, J.K.
Coupling photoisomerization of retinal to directional transport in bacteriorhodopsin.
J.Mol.Biol., 300:1237-1255, 2000

PubMed Abstract: In order to understand how isomerization of the retinal drives unidirectional transmembrane ion transport in bacteriorhodopsin, we determined the atomic structures of the BR state and M photointermediate of the E204Q mutant, to 1.7 and 1.8 A resolution, respectively. Comparison of this M, in which proton release to the extracellular surface is blocked, with the previously determined M in the D96N mutant indicates that the changes in the extracellular region are initiated by changes in the electrostatic interactions of the retinal Schiff base with Asp85 and Asp212, but those on the cytoplasmic side originate from steric conflict of the 13-methyl retinal group with Trp182 and distortion of the pi-bulge of helix G. The structural changes suggest that protonation of Asp85 initiates a cascade of atomic displacements in the extracellular region that cause release of a proton to the surface. The progressive relaxation of the strained 13-cis retinal chain with deprotonated Schiff base, in turn, initiates atomic displacements in the cytoplasmic region that cause the intercalation of a hydrogen-bonded water molecule between Thr46 and Asp96. This accounts for the lowering of the pK(a) of Asp96, which then reprotonates the Schiff base via a newly formed chain of water molecules that is extending toward the Schiff base.

PubMed: 10903866
DOI: 10.1006/jmbi.2000.3884

Experimental method

X-RAY DIFFRACTION (1.8 Å)