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PDBsum entry 1til
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Transcription
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PDB id
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1til
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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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Crystal structures of the ADP and ATP bound forms of the bacillus anti-Sigma factor spoiiab in complex with the anti-Anti-Sigma spoiiaa.
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Authors
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S.Masuda,
K.S.Murakami,
S.Wang,
C.Anders olson,
J.Donigian,
F.Leon,
S.A.Darst,
E.A.Campbell.
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Ref.
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J Mol Biol, 2004,
340,
941-956.
[DOI no: ]
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PubMed id
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Abstract
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Cell type-specific transcription during Bacillus sporulation is established by
sigma(F), the activity of which is controlled by a regulatory circuit involving
the anti-sigma factor and serine kinase SpoIIAB, and the anti-anti-sigma
SpoIIAA. When ATP is present in the nucleotide-binding site of SpoIIAB, SpoIIAA
is phosphorylated, followed by dissociation. The nucleotide-binding site of
SpoIIAB is left bound to ADP. SpoIIAB(ADP) can bind an unphosphorylated molecule
of SpoIIAA as a stable binding partner. Thus, in this circuit, SpoIIAA plays a
dual role as a substrate of the SpoIIAB kinase activity, as well as a tight
binding inhibitor. Crystal structures of both the pre-phosphorylation complex
and the inhibitory complex, SpoIIAB(ATP) and SpoIIAB(ADP) bound to SpoIIAA,
respectively, have been determined. The structural differences between the two
forms are subtle and confined to interactions with the phosphoryl groups of the
nucleotides. The structures reveal details of the SpoIIAA:SpoIIAB interactions
and how phosphorylated SpoIIAA dissociates from SpoIIAB(ADP). Finally, the
results confirm and expand upon the docking model for SpoIIAA function as an
anti-anti-sigma in releasing sigma(F) from SpoIIAB.
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Figure 7.
Figure 7. Steric clash of AA and sF on AB. The AA:AB(ATP)
complex is shown, viewed parallel with the dimer 2-fold axis, as
in Figure 2 (top), along with the corresponding position of sF
from the sF:AB(ADP) complex.11 AA and sF are shown as orange and
red a-carbon backbone worms, respectively. AB is shown as a
molecular surface. AB1 is colored cyan, AB2 is colored green,
except the surface of AB interacting with AA (4 Å cutoff),
is colored orange and the surface interacting with sF is colored
pink. The surface interacting with both binding partners
(overlap) is colored purple. Residues of AB noted as important
for docking and induced release are colored red and labeled, and
the corresponding residues on AA are drawn as stick. These pairs
include AB-Arg20:AA-Glu21, AB-Ile112:AA-Leu90, AB-ATP:AA-Ser58,
AB-Glu104:AA-Arg67. Note that the clash occurs in the area of
AB-Arg20 between AA and sF as previously predicted.[11.]
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Figure 9.
Figure 9. Model of docking during induced release. Cartoon
illustrating the mechanism of displacement of sF from AB by AA.
AB1 and AB2 are colored cyan and green, respectively. sF is
colored pink and AA in orange. Residues important for docking
and displacement are labeled in step 1. The model is as follows:
(1) AB1 of sF:AB[2] is the targeted molecule for docking as its
surface is more accessible to AA. In particular, AB-Arg20, a
residue critical for the AA:AB interaction exposed. (2) AA docks
onto its initial docking sites on AB1 (represented by AB-Glu104
and AB-Ile112). (3) AA docks into a secondary which is
represented by AA-Asp23 interacting with AB-Arg20. Upon the
second docking, a clash occurs between sF and AA (circled in
black and represented by AA-Glu21 and sF-Asp148). (4) The clash
leads to the dissociation of sF from AB(ADP). AA then slips into
its final docking conformation that is amenable to
phosphorylation (represented by AA turning yellow and Ser58
turning red). (5) P-AA dissociates from AB(ADP) due to steric
and electrostatic clashes. (6) Unphosphorylated AAs interact
with AB1 as an IC and AB2 as a target for phosphorylation.
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The above figures are
reprinted
by permission from Elsevier:
J Mol Biol
(2004,
340,
941-956)
copyright 2004.
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