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PDBsum entry 1w5e
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Cell division
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PDB id
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1w5e
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References listed in PDB file
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Key reference
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Title
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Structural insights into ftsz protofilament formation.
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Authors
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M.A.Oliva,
S.C.Cordell,
J.Löwe.
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Ref.
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Nat Struct Mol Biol, 2004,
11,
1243-1250.
[DOI no: ]
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PubMed id
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Abstract
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The prokaryotic tubulin homolog FtsZ polymerizes into a ring structure essential
for bacterial cell division. We have used refolded FtsZ to crystallize a
tubulin-like protofilament. The N- and C-terminal domains of two consecutive
subunits in the filament assemble to form the GTPase site, with the C-terminal
domain providing water-polarizing residues. A domain-swapped structure of FtsZ
and biochemical data on purified N- and C-terminal domains show that they are
independent. This leads to a model of how FtsZ and tubulin polymerization
evolved by fusing two domains. In polymerized tubulin, the nucleotide-binding
pocket is occluded, which leads to nucleotide exchange being the rate-limiting
step and to dynamic instability. In our FtsZ filament structure the nucleotide
is exchangeable, explaining why, in this filament, nucleotide hydrolysis is the
rate-limiting step during FtsZ polymerization. Furthermore, crystal structures
of FtsZ in different nucleotide states reveal notably few differences.
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Figure 4.
Figure 4. Detailed view of the intersubunit active sites in
MjFtsZ and tubulin. (a) FtsZ dimer. The GTPase domain of the
lower subunit is complemented by two aspartates (Asp235 and
Asp238) that polarize the attacking water molecule (Wat105).
Apart from these residues, which belong to loop T7, S9 and helix
H10 of the C-terminal domain of FtsZ are involved in the
protofilament contact. (b)  /
 tubulin
(PDB entry 1JFF) with -tubulin
on top (not the tubulin solution dimer, but the catalytically
active contact formed in protofilaments). The general
arrangement in the active site is very similar to that of FtsZ
with T7, S9 and H10 of the C-terminal (intermediate) domain
making the protofilament contact. Very little space would be
left for a  -phosphate,
and the polarizing acidic residue, Glu254, is not in the right
position to polarize the attacking water molecule. The tubulin
structure was solved at low resolution and exact side chain
positions may not be known for all residues.
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Figure 5.
Figure 5. A lack of conformational changes in different FtsZ
structures. (a) M. jannaschii FtsZ with bound GMPCPP at a
resolution of 2.5 Å. GDP-containing crystals were soaked
with magnesium and GMCPP in a special buffer to replace the
bound nucleotide. The -phosphate
occupies the previously identified binding pocket^6, making
hydrogen bonding contacts to loop T3. (b) Superposition of M.
jannaschii FtsZ active sites: minimal changes are observed
between the structures of monomers containing nucleotides and
the refolded, empty monomer in completely different space groups
and packing arrangements. Stereo drawing.
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The above figures are
reprinted
by permission from Macmillan Publishers Ltd:
Nat Struct Mol Biol
(2004,
11,
1243-1250)
copyright 2004.
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