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PDBsum entry 1qiv
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Calcium-binding protein
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PDB id
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1qiv
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Contents |
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* Residue conservation analysis
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References listed in PDB file
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Key reference
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Title
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A new potent calmodulin antagonist with arylalkylamine structure: crystallographic, Spectroscopic and functional studies.
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Authors
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V.Harmat,
Z.Böcskei,
G.Náray-Szabó,
I.Bata,
A.S.Csutor,
I.Hermecz,
P.Arányi,
B.Szabó,
K.Liliom,
B.G.Vértessy,
J.Ovádi.
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Ref.
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J Mol Biol, 2000,
297,
747-755.
[DOI no: ]
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PubMed id
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Abstract
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An arylalkylamine-type calmodulin antagonist, N-(3,
3-diphenylpropyl)-N'-[1-R-(3, 4-bis-butoxyphenyl)ethyl]-propylene-diamine (AAA)
is presented and its complexes with calmodulin are characterized in solution and
in the crystal. Near-UV circular dichroism spectra show that AAA binds to
calmodulin with 2:1 stoichiometry in a Ca(2+)-dependent manner. The crystal
structure with 2:1 stoichiometry is determined to 2.64 A resolution. The binding
of AAA causes domain closure of calmodulin similar to that obtained with
trifluoperazine. Solution and crystal data indicate that each of the two AAA
molecules anchors in the hydrophobic pockets of calmodulin, overlapping with two
trifluoperazine sites, i.e. at a hydrophobic pocket and an interdomain site. The
two AAA molecules also interact with each other by hydrophobic forces. A
competition enzymatic assay has revealed that AAA inhibits calmodulin-activated
phosphodiesterase activity at two orders of magnitude lower concentration than
trifluoperazine. The apparent dissociation constant of AAA to calmodulin is 18
nM, which is commensurable with that of target peptides. On the basis of the
crystal structure, we propose that the high-affinity binding is mainly due to a
favorable entropy term, as the AAA molecule makes multiple contacts in its
complex with calmodulin.
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Figure 5.
Figure 5. Structural details of AAA binding in the crystal
structure. (a) Stereo view of (2F[o] -F[c]) electron density map
contoured at the 1s level around the AAA binding sites. Carbon
atoms of the AAAs are colored magenta while AAAs and methionine
residues are labeled. (b) Comparison of the binding sites of AAA
molecules. AAA1 (left) and AAA2 (right) (lines and circles) are
shown with the interacting protein residues (lines). The
orientation of CaM is changed between the left and right panels
by fitting backbone atoms of the two domains onto each other
considering the similar fold of those. The accommodations and
conformations of the two AAAs are very similar. (c) The backbone
conformation of CaM colored from the N-terminal to the
C-terminal from blue to red with the two bound AAA molecules.
(d) Comparison of the P3[2]21 crystal structure (red) with the
P1 structure (green). The conformation of AAA changes upon the
domain motion of CaM. AAA2 and the interacting helices of the
N-terminal domain are shown with the C^a atoms of residues 92 to
144 fitted together. The molecular surface of the C-terminal
hydrophobic pocket of CaM, calculated by GRASP [Nicholls et al
1991], is shown as a chicken-wire representation (blue). The
most important interactions between AAA and CaM, shown only for
P3[2]21, are emphasized with yellow shaded lines. The black
arrow shows the change in conformation of AAA2 following the
domain motion of CaM. (a) Drawn with Bobscript v2.3 [Esnouf
1997] and (b), (c) and (d) with MOLSCRIPT v2.1 [Kraulis 1991].
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Figure 6.
Figure 6. Comparison of the AAA and TFP-binding sites of
CaM. The four TFP-binding sites, as found by [Vandonselaar et al
1994], are shown as shaded ellipses and labeled T1-T4.
Considering the structural similarity of the two domains, two
other sites (similar to T2 and T3) can be imagined, T5 and T6
(empty ellipses).
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The above figures are
reprinted
by permission from Elsevier:
J Mol Biol
(2000,
297,
747-755)
copyright 2000.
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Secondary reference #1
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Title
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Simultaneous binding of drugs with different chemical structures to ca2+-Calmodulin: crystallographic and spectroscopic studies.
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Authors
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B.G.Vertessy,
V.Harmat,
Z.Böcskei,
G.Náray-Szabó,
F.Orosz,
J.Ovádi.
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Ref.
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Biochemistry, 1998,
37,
15300-15310.
[DOI no: ]
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PubMed id
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Secondary reference #2
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Title
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Crystallization and preliminary diffraction analysis of ca(2+)-Calmodulin-Drug and apocalmodulin-Drug complexes.
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Authors
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B.G.Vertessy,
Z.Böcskei,
V.Harmath,
G.Náray-Szabó,
J.Ovádi.
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Ref.
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Proteins, 1997,
28,
131-134.
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PubMed id
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Secondary reference #3
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Title
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Trifluoperazine-Induced conformational change in ca(2+)-Calmodulin.
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Authors
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M.Vandonselaar,
R.A.Hickie,
J.W.Quail,
L.T.Delbaere.
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Ref.
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Nat Struct Biol, 1994,
1,
795-801.
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PubMed id
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Secondary reference #4
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Title
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Drug binding by calmodulin: crystal structure of a calmodulin-Trifluoperazine complex.
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Authors
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W.J.Cook,
L.J.Walter,
M.R.Walter.
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Ref.
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Biochemistry, 1994,
33,
15259-15265.
[DOI no: ]
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PubMed id
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