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PDBsum entry 3dvk
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Membrane protein
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PDB id
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3dvk
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References listed in PDB file
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Key reference
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Title
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Structures of cav2 ca2+/cam-Iq domain complexes reveal binding modes that underlie calcium-Dependent inactivation and facilitation.
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Authors
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E.Y.Kim,
C.H.Rumpf,
Y.Fujiwara,
E.S.Cooley,
F.Van petegem,
D.L.Minor.
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Ref.
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Structure, 2008,
16,
1455-1467.
[DOI no: ]
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PubMed id
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Abstract
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Calcium influx drives two opposing voltage-activated calcium channel (Ca(V))
self-modulatory processes: calcium-dependent inactivation (CDI) and
calcium-dependent facilitation (CDF). Specific Ca(2+)/calmodulin (Ca(2+)/CaM)
lobes produce CDI and CDF through interactions with the Ca(V)alpha(1) subunit IQ
domain. Curiously, Ca(2+)/CaM lobe modulation polarity appears inverted between
Ca(V)1s and Ca(V)2s. Here, we present crystal structures of Ca(V)2.1, Ca(V)2.2,
and Ca(V)2.3 Ca(2+)/CaM-IQ domain complexes. All display binding orientations
opposite to Ca(V)1.2 with a physical reversal of the CaM lobe positions relative
to the IQ alpha-helix. Titration calorimetry reveals lobe competition for a
high-affinity site common to Ca(V)1 and Ca(V)2 IQ domains that is occupied by
the CDI lobe in the structures. Electrophysiological experiments demonstrate
that the N-terminal Ca(V)2 Ca(2+)/C-lobe anchors affect CDF. Together, the data
unveil the remarkable structural plasticity at the heart of Ca(V) feedback
modulation and indicate that Ca(V)1 and Ca(V)2 IQ domains bear a dedicated CDF
site that exchanges Ca(2+)/CaM lobe occupants.
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Figure 2.
Figure 2. Ca^2+/CaM-Ca[V]2 Interaction Details
(A)
Ca[V]2.3 Ca^2+/N-lobe.
(B) Ca[V]2.2 Ca^2+/N-lobe.
(C)
Ca[V]2.3 Ca^2+/C-lobe.
(D) Ca[V]2.2 Ca^2+/C-lobe.The IQ
domain as shown in stick representation with major anchor
positions colored white. As Ca[V]2.1 and Ca[V]2.3 structures are
equivalent and the Ca[V]2.3 structure is higher resolution, we
only show Ca[V]2.3 here. Ca^2+/CaM lobes are shown in surface
representation. Residues contributing to hydrophobic (yellow),
negatively charged (red), positively charged (blue), and polar
(green) interactions (≤4 Å) to the IQ domain indicated.
Labels for IQ domain residues are boxed.
(E) Diagram of the
major Ca[V]1 and Ca[V]2 IQ domain anchor positions. The
isoleucine of the IQ motif is labeled as position 0. Ca[V]2.1,
Ca[V]2.2, and Ca[V]2.3 major anchors are shown by yellow,
purple, and orange ovals, respectively. Ca[V]1.2 anchor
positions are shown by red squares.
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Figure 3.
Figure 3. ITC Characterization of Ca^2+/CaM-Ca[V]2.1 IQ
Domain Interactions
(A) 75 μM Ca^2+/N-lobe into 7.5 μM
Ca[V]2.1 IQ domain.
(B) 75 μM Ca^2+/C-lobe into 7.5 μM
Ca[V]2.1 IQ domain.
(C) 75 μM Ca^2+/N-lobe into 7.5 μM
Ca[V]2.1 IQ domain Y1974A (position (+3)).
(D) 75 μM
Ca^2+/C-lobe into 7.5 μM Ca[V]2.1 IQ domain Y1974A (position
(+3)).
(E) 250 μM Ca^2+/C-lobe into a solution of 25 μM
Ca[V]2.1 IQ domain and 33 μM Ca^2+/N-lobe.
(F) 250 μM
Ca^2+/C-lobe into a solution of 25 μM Ca[V]2.1 IQ domain I1965A
(position (−6)), and 33 μM Ca^2+/N-lobe.
(G) 250 μM
Ca^2+/C-lobe into a solution of 25 μM Ca[V]2.1 IQ domain M1969A
(position (−2)), and 33 μM Ca^2+/N-lobe.
(H) Comparison
Ca^2+/C-lobe binding isotherms to Ca^2+/N-lobe-Ca[V]2.1 IQ
domain complexes. ITC Panels show addition of 10 μl aliquots of
titrant to the target (top) and binding isotherms (bottom).
Cartoons depict the observed binding modes. Stars indicate
mutant peptides and site of mutation.
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The above figures are
reprinted
from an Open Access publication published by Cell Press:
Structure
(2008,
16,
1455-1467)
copyright 2008.
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