1m0m
From Proteopedia
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'''BACTERIORHODOPSIN M1 INTERMEDIATE AT 1.43 A RESOLUTION''' | '''BACTERIORHODOPSIN M1 INTERMEDIATE AT 1.43 A RESOLUTION''' | ||
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[[Category: Lanyi, J K.]] | [[Category: Lanyi, J K.]] | ||
[[Category: 7-transmembrane]] | [[Category: 7-transmembrane]] | ||
| - | [[Category: | + | [[Category: Haloarchaea]] |
| - | [[Category: | + | [[Category: Ion pump]] |
| - | [[Category: | + | [[Category: Lipid]] |
| - | [[Category: | + | [[Category: Membrane protein]] |
| - | [[Category: | + | [[Category: Merohedral twinning]] |
| - | [[Category: | + | [[Category: Photoreceptor]] |
| - | [[Category: | + | [[Category: Retinal protein]] |
| - | [[Category: | + | [[Category: Serpentine]] |
| - | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 00:29:20 2008'' | |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | + | |
Revision as of 21:29, 2 May 2008
BACTERIORHODOPSIN M1 INTERMEDIATE AT 1.43 A RESOLUTION
Overview
We illuminated bacteriorhodopsin crystals at 210K to produce, in a photostationary state with 60% occupancy, the earliest M intermediate (M1) of the photocycle. The crystal structure of this state was then determined from X-ray diffraction to 1.43 A resolution. When the refined model is placed after the recently determined structure for the K intermediate but before the reported structures for two later M states, a sequence of structural changes becomes evident in which movements of protein atoms and bound water are coordinated with relaxation of the initially strained photoisomerized 13-cis,15-anti retinal. In the K state only retinal atoms are displaced, but in M1 water 402 moves also, nearly 1A away from the unprotonated retinal Schiff base nitrogen. This breaks the hydrogen bond that bridges them, and initiates rearrangements of the hydrogen-bonded network of the extracellular region that develop more fully in the intermediates that follow. In the M1 to M2 transition, relaxation of the C14-C15 and C15=NZ torsion angles to near 180 degrees reorients the retinylidene nitrogen atom from the extracellular to the cytoplasmic direction, water 402 becomes undetectable, and the side-chain of Arg82 is displaced strongly toward Glu194 and Glu204. Finally, in the M2 to M2' transition, correlated with release of a proton to the extracellular surface, the retinal assumes a virtually fully relaxed bent shape, and the 13-methyl group thrusts against the indole ring of Trp182 which tilts in the cytoplasmic direction. Comparison of the structures of M1 and M2 reveals the principal switch in the photocycle: the change of the angle of the C15=NZ-CE plane breaks the connection of the unprotonated Schiff base to the extracellular side and establishes its connection to the cytoplasmic side.
About this Structure
1M0M is a Single protein structure of sequence from Halobacterium salinarum. Full crystallographic information is available from OCA.
Reference
Crystallographic structure of the retinal and the protein after deprotonation of the Schiff base: the switch in the bacteriorhodopsin photocycle., Lanyi J, Schobert B, J Mol Biol. 2002 Aug 23;321(4):727-37. PMID:12206786 Page seeded by OCA on Sat May 3 00:29:20 2008
