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PDBsum entry 3dof
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Signaling protein/hydrolase
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PDB id
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3dof
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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 arl2-Gtp-Bart complex reveals a novel recognition and binding mode of small gtpase with effector.
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Authors
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T.Zhang,
S.Li,
Y.Zhang,
C.Zhong,
Z.Lai,
J.Ding.
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Ref.
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Structure, 2009,
17,
602-610.
[DOI no: ]
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PubMed id
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Abstract
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ARL2 is a member of the ADP-ribosylation factor family but has unique
biochemical features. BART is an effector of ARL2 that is essential for nuclear
retention of STAT3 and may also be involved in mitochondria transport and
apoptosis. Here we report the crystal structure and biochemical characterization
of human ARL2-GTP-BART complex. ARL2-GTP assumes a typical small GTPase fold
with a unique N-terminal alpha helix conformation. BART consists of a six alpha
helix bundle. The interactions between ARL2 and BART involve two interfaces: a
conserved N-terminal LLXIL motif of ARL2 is embedded in a hydrophobic cleft of
BART and the switch regions of ARL2 interact with helix alpha3 of BART. Both
interfaces are essential for the binding as verified by mutagenesis study. This
novel recognition and binding mode is different from that of other small
GTPase-effector interactions and provides molecular basis for the high
specificity of ARL2 for BART.
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Figure 1.
Figure 1. Structure of the ARL2-GTP-BART Complex
(A) A
stereo view of the ARL2-GTP-BART complex. ARL2 is colored in
yellow with the N-terminal α helix in cyan and the switch I,
switch II, and inter-switch regions in magenta, orange, and
blue, respectively. The bound GTP is shown with a ball-and-stick
model and the Mg^2+ ion in a green sphere. BART is colored in
green with the secondary structures labeled.
(B) A stereo
view of a representative difference Fourier Fo-Fc map (2σ
contour level) in the interaction interface of the ARL2-BART
complex in the region of helix α1 of ARL2 and helix α4 of
BART.
(C) Superposition of ARL2-GTP in the ARL2-GTP-BART
(red) and ARL2-GTP-PDEδ complexes (blue) and ARL3-GDP (yellow)
showing the overall conformational differences.
(D)
Superposition of the crystal structure of BART in the
ARL2-GTP-BART complex (green) and the NMR solution structure of
BART alone (yellow) showing the overall conformational
differences.
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Figure 2.
Figure 2. Interactions between ARL2-GTP and BART
(A) A
stereo view showing the interactions between ARL2 and BART at
interface I. Helix α1 of ARL2 (cyan) is embedded in a
hydrophobic cleft formed by helices α3, α4, and α5 of BART
(green).
(B) A stereo view showing the interactions between
ARL2 and BART at interface II. The switch regions of ARL2
(switches I and II and the inter-switch region in magenta,
orange, and blue, respectively) have both hydrophobic and
hydrophilic interactions with the N terminus of helix α3 and
the following loop of BART (green). The hydrogen-bonding
interactions are indicated by dashed lines.
(C) A schematic
diagram showing the hydrophobic contacts between ARL2 and BART.
(D) A schematic diagram showing the hydrogen-bonding
interactions between ARL2 and BART.
(E) In vitro binding
assay of the wild-type and mutant ARL2 with the GST-fused
wild-type BART. GST cannot bind to ARL2 and thus was used as the
negative control.
(F) In vitro binding assay of the
wild-type ARL2 with the GST-fused wild-type and mutant BART.
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The above figures are
reprinted
by permission from Cell Press:
Structure
(2009,
17,
602-610)
copyright 2009.
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