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PDBsum entry 2p0h
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Ligand binding protein
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PDB id
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2p0h
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References listed in PDB file
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Key reference
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Title
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Non-Canonical interaction of phosphoinositides with pleckstrin homology domains of tiam1 and arhgap9.
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Authors
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D.F.Ceccarelli,
I.M.Blasutig,
M.Goudreault,
Z.Li,
J.Ruston,
T.Pawson,
F.Sicheri.
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Ref.
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J Biol Chem, 2007,
282,
13864-13874.
[DOI no: ]
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PubMed id
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Abstract
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Pleckstrin homology (PH) domains are phosphoinositide (PI)-binding modules that
target proteins to membrane surfaces. Here we define a family of PH domain
proteins, including Tiam1 and ArhGAP9, that demonstrates specificity for
PI(4,5)P(2), as well as for PI(3,4,5)P(3) and PI(3,4)P(2), the products of PI
3-kinase. These PH domain family members utilize a non-canonical
phosphoinositide binding pocket related to that employed by beta-spectrin.
Crystal structures of the PH domain of ArhGAP9 in complex with the headgroups of
Ins(1,3,4)P(3), Ins(1,4,5)P(3), and Ins(1,3,5)P(3) reveal how two adjacent
phosphate positions in PI(3,4)P(2), PI(4,5)P(2), and PI(3,4,5)P(3) are
accommodated through flipped conformations of the bound phospholipid. We
validate the non-canonical site of phosphoinositide interaction by showing that
binding pocket mutations, which disrupt phosphoinositide binding in vitro, also
disrupt membrane localization of Tiam1 in cells. We posit that the diversity in
PI interaction modes displayed by PH domains contributes to their versatility of
use in biological systems.
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Figure 7.
FIGURE 7. Stereographic view of AG9 PH domain binding to
Ins(1,4,5)P[3] (A), Ins(1,3,4)P[3] (B), and Ins(1,3,5)P[3] (C).
Experimental F[o] - F[c] electron density map prior to modeling
of bound ligand is shown as a wire mesh contoured at 2.5 sigma.
PI-interacting residues are shown as stick models with hydrogen
bonds indicated by dashed lines. Phosphate positions of the
inositol ring are labeled. Water molecules are indicated by red
spheres. In C only a single phosphate moiety of the Ins(1,3,5)P3
ligand is modeled.
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Figure 8.
FIGURE 8. Superimposed stereographic view of the AG9^145
and AG9^134 PI binding pockets in complex with Ins(1,4,5)P[3]
and Ins(1,3,4)P[3], respectively. The PH domain of AG9^145 is
colored cyan with bound Ins(1,4,5)P[3] in purple; the AG9^134 PH
domain is colored green with bound Ins(1,3,4)P[3] in pink.
Orientation of bound PI(4,5)P[2] and PI(3,4)P[2] are related by
a rotation of  180° about the P1-P4
axis of the inositol ring.
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The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(2007,
282,
13864-13874)
copyright 2007.
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