 |
PDBsum entry 1u27
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Lipid binding protein
|
PDB id
|
|
|
|
1u27
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
References listed in PDB file
|
|
|
Key reference
|
|
|
Title
|
|
Structural determinants of phosphoinositide selectivity in splice variants of grp1 family ph domains.
|
|
|
Authors
|
|
T.C.Cronin,
J.P.Dinitto,
M.P.Czech,
D.G.Lambright.
|
|
|
Ref.
|
|
EMBO J, 2004,
23,
3711-3720.
[DOI no: ]
|
|
|
PubMed id
|
|
|
|
|
|
Abstract
|
|
|
The pleckstrin homology (PH) domains of the homologous proteins Grp1 (general
receptor for phosphoinositides), ARNO (Arf nucleotide binding site opener), and
Cytohesin-1 bind phosphatidylinositol (PtdIns) 3,4,5-trisphosphate with
unusually high selectivity. Remarkably, splice variants that differ only by the
insertion of a single glycine residue in the beta1/beta2 loop exhibit dual
specificity for PtdIns(3,4,5)P(3) and PtdIns(4,5)P(2). The structural basis for
this dramatic specificity switch is not apparent from the known modes of
phosphoinositide recognition. Here, we report crystal structures for dual
specificity variants of the Grp1 and ARNO PH domains in either the unliganded
form or in complex with the head groups of PtdIns(4,5)P(2) and
PtdIns(3,4,5)P(3). Loss of contacts with the beta1/beta2 loop with no
significant change in head group orientation accounts for the significant
decrease in PtdIns(3,4,5)P(3) affinity observed for the dual specificity
variants. Conversely, a small increase rather than decrease in affinity for
PtdIns(4,5)P(2) is explained by a novel binding mode, in which the glycine
insertion alleviates unfavorable interactions with the beta1/beta2 loop. These
observations are supported by a systematic mutational analysis of the
determinants of phosphoinositide recognition.
|
|
|
|
|
|
|
|
Figure 5.
Figure 5 Comparison with other PH domain structures. (A) Overlay
of the 3G ARNO PH domain (semitransparent) and PLC  PH
domain (PDB ID code: 1MAI), both in complex with Ins(1,4,5)P[3],
following superposition of C  atoms.
Ins(1,4,5)P[3]is depicted in red (3G ARNO) and yellow (PLC ).
(B) Schematic diagram illustrating the approximate rigid body
and torsion angle rotations that transform Ins(1,4,5)P[3] from
the orientation in the PLC PH
domain to that in the 3G ARNO PH domain. (C) Overlay of
Ins(1,4,5)P[3] bound to the 3G ARNO PH domain with the electron
density corresponding to inorganic sulfate ions from the
unliganded 3G Grp1 PH domain following superposition of C atoms.
The electron density is from  A
weighted F[o] -F[c] and 2F[o] -F[c] maps contoured at 3.0 and
1.2 ,
respectively. The maps were generated as in Figure 2C. (D)
Overlay of the 2G Grp1 PH domain (semitransparent) and the PKB
PH domain (PDB ID code: 1H10), both in complex with
Ins(1,3,4,5)P[4], following superposition of C atoms.
Ins(1,3,4,5)P[4] is depicted in yellow (2G Grp1) and green (PKB).
|
|
Figure 6.
Figure 6 Observed and hypothetical modes of polyphosphoinositide
recognition. Schematic diagram depicting potential modes of
polyphosphoinositide recognition by PH domains. The orientation
of the inositol ring and disposition of phosphate groups are
categorized with respect to the location of inorganic
sulfate/phosphate ions observed in the unliganded structures of
the 2G Grp1 and Dapp1 PH domains. Blue circles represent the
phosphate binding site corresponding to the most buried and
electropositive region of the head group binding site formed
primarily by the N-terminal lysine and C-terminal arginine
residue of the signature motif. Yellow circles represent the
phosphate binding site comprised of the N-terminal lysine
residue from the signature motif as well as basic and/or polar
residues from the variable SDRs. In this classification of
binding modes, rotational and/or translational displacements of
the inositol ring that are not sufficiently large to alter the
network of interactions with conserved residues are neglected as
are the specific rotomer conformations of the phosphate groups.
|
|
|
|
|
|
The above figures are
reprinted
from an Open Access publication published by Macmillan Publishers Ltd:
EMBO J
(2004,
23,
3711-3720)
copyright 2004.
|
|
|
|
|
|
|
