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PDBsum entry 2k3h
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Protein transport
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PDB id
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2k3h
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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 determinants for ca2+ and phosphatidylinositol 4,5-Bisphosphate binding by the c2a domain of rabphilin-3a.
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Authors
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N.Coudevylle,
P.Montaville,
A.Leonov,
M.Zweckstetter,
S.Becker.
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Ref.
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J Biol Chem, 2008,
283,
35918-35928.
[DOI no: ]
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PubMed id
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Abstract
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Rabphilin-3A is a neuronal C2 domain tandem containing protein involved in
vesicle trafficking. Both its C2 domains (C2A and C2B) are able to bind
phosphatidylinositol 4,5-bisphosphate, a key player in the neurotransmitter
release process. The rabphilin-3A C2A domain has previously been shown to bind
inositol-1,4,5-trisphosphate (IP3; phosphatidylinositol 4,5-bisphosphate
headgroup) in a Ca(2+)-dependent manner with a relatively high affinity (50 mum)
in the presence of saturating concentrations of Ca(2+). Moreover, IP3 and Ca(2+)
binding to the C2A domain mutually enhance each other. Here we present the
Ca(2+)-bound solution structure of the C2A domain. Structural comparison with
the previously published Ca(2+)-free crystal structure revealed that Ca(2+)
binding induces a conformational change of Ca(2+) binding loop 3 (CBL3). Our IP3
binding studies as well as our IP3-C2A docking model show the active involvement
of CBL3 in IP3 binding, suggesting that the conformational change on CBL3 upon
Ca(2+) binding enables the interaction with IP3 and vice versa, in line with a
target-activated messenger affinity mechanism. Our data provide detailed
structural insight into the functional properties of the rabphilin-3A C2A domain
and reveal for the first time the structural determinants of a target-activated
messenger affinity mechanism.
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Figure 2.
Overall solution structure of the Ca^2^+-bound rabphilin-3A
C2A domain. A, backbone superimposition of the final set of 20
structures for the C2A domain. B, representative ribbon model of
the C2A domain. Ca^2+ ions are depicted as blue spheres.
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Figure 4.
Structure comparison of the Ca^2^+-bound form and Ca^2^+-free
form of the rabphilin-3A C2A domain. A, backbone superposition
of the Ca^2+-bound solution structure of the C2A domain (in
blue) with the Ca^2+-free crystal structure (in gray). B, Ca^2+
binding site comparison of the Ca^2+-bound form (in blue) with
the Ca^2+-free form (in gray). Backbones are represented by
ribbons, side chains of residues involved in Ca^2+ binding are
represented by sticks, and Ca^2+ ions are depicted as blue
spheres. C, comparison of the CBL3 conformation in the
Ca^2+-bound (blue) and Ca^2+-free (gray) form of the C2A domain.
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The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(2008,
283,
35918-35928)
copyright 2008.
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