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PDBsum entry 1v2z
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Circadian clock protein
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PDB id
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1v2z
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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 structure of the c-Terminal clock-Oscillator domain of the cyanobacterial kaia protein.
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Authors
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T.Uzumaki,
M.Fujita,
T.Nakatsu,
F.Hayashi,
H.Shibata,
N.Itoh,
H.Kato,
M.Ishiura.
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Ref.
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Nat Struct Mol Biol, 2004,
11,
623-631.
[DOI no: ]
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PubMed id
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Abstract
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KaiA, KaiB and KaiC constitute the circadian clock machinery in cyanobacteria,
and KaiA activates kaiBC expression whereas KaiC represses it. Here we show that
KaiA is composed of three functional domains, the N-terminal amplitude-amplifier
domain, the central period-adjuster domain and the C-terminal clock-oscillator
domain. The C-terminal domain is responsible for dimer formation, binding to
KaiC, enhancing KaiC phosphorylation and generating the circadian oscillations.
The X-ray crystal structure at a resolution of 1.8 A of the C-terminal
clock-oscillator domain of KaiA from the thermophilic cyanobacterium
Thermosynechococcus elongatus BP-1 shows that residue His270, located at the
center of a KaiA dimer concavity, is essential to KaiA function. KaiA binding to
KaiC probably occurs via the concave surface. On the basis of the structure, we
predict the structural roles of the residues that affect circadian oscillations.
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Figure 3.
Figure 3. Synechococcus KaiA dimerization assayed by gel
filtration chromatography. Full-length (a), N- and central
domains (b), C-terminal domain (c), central and C-terminal
domains (d) and N- and C-terminal domains (e).
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Figure 6.
Figure 6. Overview of the structure of T. elongatus KaiA(174
-283) (the C-terminal clock-oscillator domain). (a) C  backbone
of a KaiA(174 -283) subunit. h1 (residues 174 -181), red; h2
(186 -203), orange; h3 (211 -225), pink; h4 (229 -247), green;
h5 (255 -258), blue; h6 (260 -277), cyan. (b) A hydrophobic core
formed by Phe177, Phe178, Phe223, Phe224 and Tyr275 connecting
h1, h3 and h6. The helices are colored as described above. The
residues are in ball-and-stick representation (black, carbon;
red, oxygen; yellow, sulfur). (c) A hydrophobic core formed by
Tyr197, Tyr204, Phe205, Phe218, Met240, Phe243, Leu257, Tyr260
and Leu264. (d) C backbone
of a dimer. Yellow, A-chain; purple, B-chain. The eight residues
(Arg179, Asp226, Ile227, Val229, Asp259, Arg261, Glu273 and
Arg276) involved in dimer formation are indicated in
ball-and-stick, as are the functionally essential residue
(His270) and its neighboring residues (Asp266 and Tyr204).
Carbon, black; nitrogen, blue; oxygen, red. Green dotted lines,
hydrogen bonds involved in dimer formation; cyan dotted lines,
hydrogen bonds connecting His270, Asp266 and Tyr204, linearly
arrayed. (e) Space-filling representation of a dimer. The 23
residues conserved in the 11 strains are green, except for
His270, which is red. (f) View of e from a different angle.
Figures of molecular models were prepared with MolScript34 and
Raster3D^35.
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The above figures are
reprinted
by permission from Macmillan Publishers Ltd:
Nat Struct Mol Biol
(2004,
11,
623-631)
copyright 2004.
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