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PDBsum entry 1jv6
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Ion transport
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PDB id
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1jv6
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Contents |
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* Residue conservation analysis
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References listed in PDB file
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Key reference
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Title
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Crystal structure of the d85s mutant of bacteriorhodopsin: model of an o-Like photocycle intermediate.
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Authors
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S.Rouhani,
J.P.Cartailler,
M.T.Facciotti,
P.Walian,
R.Needleman,
J.K.Lanyi,
R.M.Glaeser,
H.Luecke.
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Ref.
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J Mol Biol, 2001,
313,
615-628.
[DOI no: ]
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PubMed id
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Abstract
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Crystal structures are reported for the D85S and D85S/F219L mutants of the
light-driven proton/hydroxyl-pump bacteriorhodopsin. These mutants crystallize
in the orthorhombic C222(1) spacegroup, and provide the first demonstration that
monoolein-based cubic lipid phase crystallization can support the growth of
well-diffracting crystals in non-hexagonal spacegroups. Both structures exhibit
similar and substantial differences relative to wild-type bacteriorhodopsin,
suggesting that they represent inherent features resulting from neutralization
of the Schiff base counterion Asp85. We argue that these structures provide a
model for the last photocycle intermediate (O) of bacteriorhodopsin, in which
Asp85 is protonated, the proton release group is deprotonated, and the retinal
has reisomerized to all-trans. Unlike for the M and N photointermediates, where
structural changes occur mainly on the cytoplasmic side, here the large-scale
changes are confined to the extracellular side. As in the M intermediate, the
side-chain of Arg82 is in a downward configuration, and in addition, a pi-cloud
hydrogen bond forms between Trp189 NE1 and Trp138. On the cytoplasmic side,
there is increased hydration near the surface, suggesting how Asp96 might
communicate with the bulk during the rise of the O intermediate.
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Figure 5.
Figure 5. View of the extracellu-
lar side, showing an extensive
hydrogen-bonding network of side-
chains and water molecules, as
well as the alternate conformation
of Glu194. Not only is the hydro-
gen-bonding network between the
Schiff base and the proton release
group broken, but Arg82 is now in
a downward configuration with
hydrogen bonds towards the pro-
ton release group similar to what is
observed for M intermediates.
Somewhat long hydrogen bonds
exist from Arg82-NH2 to water 408
(3.44 Å ) and from Arg82-NH1 to
water 409 (3.25 Å ).
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Figure 7.
Figure 7. View of the cyto-
plasmic side, showing Phe42 acting
as a barrier between Asp96 and the
bulk aqueous phase. This region
contains numerous ordered water
molecules that form a hydrogen-
bonding network and are likely to
be involved in the reprotonation of
Asp96 during the N
!
O tran-
sition.
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The above figures are
reprinted
by permission from Elsevier:
J Mol Biol
(2001,
313,
615-628)
copyright 2001.
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