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PDBsum entry 1h4x
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Cell differentiation
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PDB id
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1h4x
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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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Structure of the bacillus cell fate determinant spoiiaa in phosphorylated and unphosphorylated forms.
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Authors
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P.R.Seavers,
R.J.Lewis,
J.A.Brannigan,
K.H.Verschueren,
G.N.Murshudov,
A.J.Wilkinson.
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Ref.
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Structure, 2001,
9,
605-614.
[DOI no: ]
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PubMed id
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Abstract
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BACKGROUND: The asymmetric cell division during sporulation in Bacillus subtilis
gives rise to two compartments: the mother cell and the forespore. Each follow
different programs of gene expression coordinated by a succession of alternate
RNA polymerase sigma factors. The activity of the first of these sigma factors,
sigmaF, is restricted to the forespore although sigmaF is present in the
predivisional cell and partitions into both compartments following the
asymmetric septation. For sigmaF to become active, it must escape from a complex
with its cognate anti-sigma factor, SpoIIAB. This relief from SpoIIAB inhibition
requires the dephosphorylation of the anti-sigma factor antagonist, SpoIIAA. The
phosphorylation state of SpoIIAA is thus a key determinant of sigmaF activity
and cell fate. RESULTS: We have solved the crystal structures of SpoIIAA from
Bacillus sphaericus in its phosphorylated and unphosphorylated forms. The
overall structure consists of a central beta-pleated sheet, one face of which is
buried by a pair of alpha helices, while the other is largely exposed to
solvent. The site of phosphorylation, Ser57, is located at the N terminus of
helix alpha2. The phosphoserine is exceptionally well defined in the 1.2 A
electron density maps, revealing that the structural changes accompanying
phosphorylation are slight. CONCLUSIONS: Comparison of unphosphorylated and
phosphorylated SpoIIAA shows that covalent modification has no significant
effect on the global structure of the protein. The phosphoryl group has a
passive role as a negatively charged flag rather than the active role it plays
as a nucleus of structural reorganization in many eukaryotic signaling systems.
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Figure 2.
Figure 2. The Overall Fold of SpoIIAA(a) Ribbon tracing
with the C[a] and side chain atoms of Ser57 shown in
ball-and-stick.(b) Stereo C[a] trace with the N- and C-termini
and every 10^th residue labeled. This and subsequent figures
were drawn with the program MOLSCRIPT [49]
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The above figure is
reprinted
by permission from Cell Press:
Structure
(2001,
9,
605-614)
copyright 2001.
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