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PDBsum entry 3cx6
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Signaling protein
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PDB id
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3cx6
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References listed in PDB file
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Key reference
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Title
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Recognition of the activated states of galpha13 by the rgrgs domain of pdzrhogef.
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Authors
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Z.Chen,
W.D.Singer,
S.M.Danesh,
P.C.Sternweis,
S.R.Sprang.
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Ref.
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Structure, 2008,
16,
1532-1543.
[DOI no: ]
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PubMed id
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Abstract
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G12 class heterotrimeric G proteins stimulate RhoA activation by RGS-RhoGEFs.
However, p115RhoGEF is a GTPase Activating Protein (GAP) toward Galpha13,
whereas PDZRhoGEF is not. We have characterized the interaction between the
PDZRhoGEF rgRGS domain (PRG-rgRGS) and the alpha subunit of G13 and have
determined crystal structures of their complexes in both the inactive state
bound to GDP and the active states bound to GDP*AlF (transition state) and
GTPgammaS (Michaelis complex). PRG-rgRGS interacts extensively with the helical
domain and the effector-binding sites on Galpha13 through contacts that are
largely conserved in all three nucleotide-bound states, although PRG-rgRGS has
highest affinity to the Michaelis complex. An acidic motif in the N terminus of
PRG-rgRGS occupies the GAP binding site of Galpha13 and is flexible in the
GDP*AlF complex but well ordered in the GTPgammaS complex. Replacement of key
residues in this motif with their counterparts in p115RhoGEF confers GAP
activity.
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Figure 3.
Figure 3. GTPase Active Site in the
PRG-rgRGS:Gα13•GDP•AlF[4]^− Complex
(A) Electron
density (cages) at the active site from a 2.25 Å
σ[A]−weighted 2F[o]−F[c] difference map (Read, 1986) is
contoured at 1.6 standard deviations above the mean. Only
densities of the PRG-rgRGS N terminus, GDP•Mg^2+•AlF[4]^−
and the axial water molecule bound to AlF[4]^− are shown.
Hydrogen bonds are drawn as dotted lines.
(B) Structural
comparison of active sites from
PRG-rgRGS:Gα13•GDP•AlF[4]^− complex and
p115-rgRGS:Gα13/i1•GDP•AlF[4]^− complex. Elements from
Gα13/i1 are colored gray and the N terminus of p115-rgRGS is
colored brown.
(C) Stimulation of GTPase activity of Gα13
by increasing concentrations of wild-type and mutated PRG-rgRGS.
Amino acids mutated in PRG-rgRGS are colored red.
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Figure 5.
Figure 5. The Interface Between the RGS-Box and C-Terminal
Extension of PRG-rgRGS and Gα13
(A) The solvent accessible
surface of Gα13 is colored as in Figure 1C, with residues
contacting the rgRGS colored blue. The RGS-box and C-terminal
extension is colored green, with elements contacting Gα13
colored red.
(B) Residues of Gα13 that contact PRG-rgRGS
are colored according to electrostatic potential as in Figure
2A. Side chains from PRG-rgRGS that directly contact Gα13 are
represented as ball-and-stick models. In addition to the αE
helix, the α3-α4 and α10-α11 loops of PRG-rgRGS also
directly contact the effector-binding site of Gα13.
(C)
Differences at the effector-binding site on Gα13 upon binding
to PRG-rgRGS (left) or p115-rgRGS (right). Residues directly
involved in the rgRGS:Gα13 interface are represented as
ball-and-stick models.
(D) Ribbon diagram depicting the
interaction interface between switch II of Gα13 and the
N-terminal and the RGS-box subdomains of PRG-rgRGS. Main chain
and side chain atoms are represented as ball-and-stick models.
Hydrogen bonds are drawn as dotted lines.
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The above figures are
reprinted
from an Open Access publication published by Cell Press:
Structure
(2008,
16,
1532-1543)
copyright 2008.
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