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PDBsum entry 2r09
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Signaling protein
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PDB id
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2r09
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References listed in PDB file
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Key reference
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Title
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Structural basis and mechanism of autoregulation in 3-Phosphoinositide-Dependent grp1 family arf gtpase exchange factors.
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Authors
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J.P.Dinitto,
A.Delprato,
M.T.Gabe lee,
T.C.Cronin,
S.Huang,
A.Guilherme,
M.P.Czech,
D.G.Lambright.
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Ref.
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Mol Cell, 2007,
28,
569-583.
[DOI no: ]
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PubMed id
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Abstract
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Arf GTPases regulate membrane trafficking and actin dynamics. Grp1, ARNO, and
Cytohesin-1 comprise a family of phosphoinositide-dependent Arf GTPase exchange
factors with a Sec7-pleckstrin homology (PH) domain tandem. Here, we report that
the exchange activity of the Sec7 domain is potently autoinhibited by conserved
elements proximal to the PH domain. The crystal structure of the Grp1 Sec7-PH
tandem reveals a pseudosubstrate mechanism of autoinhibition in which the linker
region between domains and a C-terminal amphipathic helix physically block the
docking sites for the switch regions of Arf GTPases. Mutations within either
element result in partial or complete activation. Critical determinants of
autoinhibition also contribute to insulin-stimulated plasma membrane
recruitment. Autoinhibition can be largely reversed by binding of active Arf6 to
Grp1 and by phosphorylation of tandem PKC sites in Cytohesin-1. These
observations suggest that Grp1 family GEFs are autoregulated by mechanisms that
depend on plasma membrane recruitment for activation.
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Figure 3.
Figure 3. Pseudosubstrate Autoinhibition by the Sec7-PH
Linker and C-Terminal Helix
(A) Intramolecular interactions
at the interface between the linker and Sec7 domain.
(B)
Intramolecular interactions at the interface between the
C-terminal helix and Sec7 domain.
(C and D) Comparison of
the linker and C-terminal helix of Grp1 with the switch I and II
regions of Arf1-GDP from the complex with the E156K mutant of
the ARNO Sec7 domain (PDB ID code 1R8S) after superposition of
Cα atoms.
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Figure 7.
Figure 7. Model for Autoregulation of Grp1 Family GEFs
After PtdIns(3,4,5)P[3]-dependent plasma membrane recruitment of
Grp1 family GEFs, lateral association with Arf6-GTP
simultaneously enhances membrane partitioning and shifts the
equilibrium toward the catalytically competent conformation.
Other mechanisms, including phosphorylation of PKC sites in the
polybasic motif of Cytohesin-1, may be required for full
activation.
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The above figures are
reprinted
from an Open Access publication published by Cell Press:
Mol Cell
(2007,
28,
569-583)
copyright 2007.
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