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PDBsum entry 2i94
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Protein binding
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PDB id
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2i94
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References listed in PDB file
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Key reference
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Title
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Structural basis for calcium-Induced inhibition of rhodopsin kinase by recoverin.
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Authors
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J.B.Ames,
K.Levay,
J.N.Wingard,
J.D.Lusin,
V.Z.Slepak.
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Ref.
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J Biol Chem, 2006,
281,
37237-37245.
[DOI no: ]
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PubMed id
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Abstract
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Recoverin, a member of the neuronal calcium sensor branch of the EF-hand
superfamily, serves as a calcium sensor that regulates rhodopsin kinase (RK)
activity in retinal rod cells. We report here the NMR structure of Ca(2+)-bound
recoverin bound to a functional N-terminal fragment of rhodopsin kinase
(residues 1-25, called RK25). The overall main-chain structure of recoverin in
the complex is similar to structures of Ca(2+)-bound recoverin in the absence of
target (<1.8A root-mean-square deviation). The first eight residues of
recoverin at the N terminus are solvent-exposed, enabling the N-terminal
myristoyl group to interact with target membranes, and Ca(2+) is bound at the
second and third EF-hands of the protein. RK25 in the complex forms an
amphipathic helix (residues 4-16). The hydrophobic face of the RK25 helix
(Val-9, Val-10, Ala-11, Ala-14, and Phe-15) interacts with an exposed
hydrophobic groove on the surface of recoverin lined by side-chain atoms of
Trp-31, Phe-35, Phe-49, Ile-52, Tyr-53, Phe-56, Phe-57, Tyr-86, and Leu-90.
Residues of recoverin that contact RK25 are highly conserved, suggesting a
similar target binding site structure in all neuronal calcium sensor proteins.
Site-specific mutagenesis and deletion analysis confirm that the hydrophobic
residues at the interface are necessary and sufficient for binding. The
recoverin-RK25 complex exhibits Ca(2+)-induced binding to rhodopsin immobilized
on concanavalin-A resin. We propose that Ca(2+)-bound recoverin is bound between
rhodopsin and RK in a ternary complex on rod outer segment disk membranes,
thereby blocking RK interaction with rhodopsin at high Ca(2+).
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Figure 5.
FIGURE 5. Intermolecular interactions between recoverin and
RK25. Side-chain atoms in the hydrophobic groove of recoverin
(yellow) interact with side-chain atoms from the hydrophobic
surface of RK25 helix (magenta).
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Figure 7.
FIGURE 7. Schematic model of Ca^2+-induced inhibition of
rhodopsin kinase. Myristoylation (red) targets Ca^2+-bound
recoverin to the membrane surface, where it interacts with
rhodopsin. Recoverin also interacts with the N-terminal helix of
rhodopsin kinase (magenta), forming a ternary complex on the
membrane surface that blocks phosphorylation of rhodopsin. Light
activation leads to a lowering of cytosolic Ca^2+, causing
conformational changes in recoverin that sequester the
covalently attached myristoyl group and disrupt the interaction
with rhodopsin kinase. Ca^2+-free recoverin then dissociates
from the membrane surface, allowing RK to phosphorylate the
C-terminal tail of light-excited rhodopsin.
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The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(2006,
281,
37237-37245)
copyright 2006.
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