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PDBsum entry 2esm
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References listed in PDB file
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Key reference
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Title
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The structure of dimeric rock i reveals the mechanism for ligand selectivity.
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Authors
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M.Jacobs,
K.Hayakawa,
L.Swenson,
S.Bellon,
M.Fleming,
P.Taslimi,
J.Doran.
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Ref.
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J Biol Chem, 2006,
281,
260-268.
[DOI no: ]
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PubMed id
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Abstract
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ROCK or Rho-associated kinase, a serine/threonine kinase, is an effector of
Rho-dependent signaling and is involved in actin-cytoskeleton assembly and cell
motility and contraction. The ROCK protein consists of several domains: an
N-terminal region, a kinase catalytic domain, a coiled-coil domain containing a
RhoA binding site, and a pleckstrin homology domain. The C-terminal region of
ROCK binds to and inhibits the kinase catalytic domains, and this inhibition is
reversed by binding RhoA, a small GTPase. Here we present the structure of the
N-terminal region and the kinase domain. In our structure, two N-terminal
regions interact to form a dimerization domain linking two kinase domains
together. This spatial arrangement presents the kinase active sites and
regulatory sequences on a common face affording the possibility of both kinases
simultaneously interacting with a dimeric inhibitory domain or with a dimeric
substrate. The kinase domain adopts a catalytically competent conformation;
however, no phosphorylation of active site residues is observed in the
structure. We also determined the structures of ROCK bound to four different
ATP-competitive small molecule inhibitors (Y-27632, fasudil, hydroxyfasudil, and
H-1152P). Each of these compounds binds with reduced affinity to cAMP-dependent
kinase (PKA), a highly homologous kinase. Subtle differences exist between the
ROCK- and PKA-bound conformations of the inhibitors that suggest that
interactions with a single amino acid of the active site (Ala215 in ROCK and
Thr183 in PKA) determine the relative selectivity of these compounds.
Hydroxyfasudil, a metabolite of fasudil, may be selective for ROCK over PKA
through a reversed binding orientation.
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Figure 1.
FIGURE 1. Overall structure of the ROCK/Y-27632 complex. A,
the ROCK protein dimer is drawn with  -sheets as arrows and
 -helices as cylinders.
One monomer is drawn in gray, and the others are colored by
protein region. The N-terminal dimerization domain is shown in
red. The N-terminal kinase domain (dark blue) is shown with the
glycine-rich loop drawn in green. The hinge connecting the two
domains is colored orange. The C-terminal kinase domain is shown
in light blue with the activation loop in purple and the kinase
tail in yellow. Y-27632 is shown in the active site near the
glycine-rich loop and the hinge. B, a surface representation of
the dimer is shown where both monomers are colored by region.
Y-27632 is shown in the active site as spheres. A model of the
substrate peptide is shown as a pink cylinder and strand, based
upon a superposition of the ROCK structure and the
PKA/ATP/peptide complex (Protein Data Bank code 1ATP [PDB]
). C and D, an expanded view of the dimerization domain is shown
in two orientations, differing by a 90° rotation. All of the
structure figures were made with PYMOL (58).
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Figure 3.
FIGURE 3. Phosphothreonine-binding site in PKA aligned with
ROCK. The activation loops of PKA (gray) and ROCK (green) are
shown with interactions between side chains and the phosphate
shown as purple dotted lines.
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The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(2006,
281,
260-268)
copyright 2006.
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