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PDBsum entry 2i3s
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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 analysis of bub3 interactions in the mitotic spindle checkpoint.
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Authors
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N.A.Larsen,
J.Al-Bassam,
R.R.Wei,
S.C.Harrison.
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Ref.
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Proc Natl Acad Sci U S A, 2007,
104,
1201-1206.
[DOI no: ]
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PubMed id
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Abstract
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The Mad3/BubR1, Mad2, Bub1, and Bub3 proteins are gatekeepers for the transition
from metaphase to anaphase. Mad3 from Saccharomyces cerevisiae has homology to
Bub1 but lacks a corresponding C-terminal kinase domain. Mad3 forms a stable
heterodimer with Bub3. Negative-stain electron microscopy shows that Mad3 is an
extended molecule (approximately 200 A long), whereas Bub3 is globular. The
Gle2-binding-sequence (GLEBS) motifs found in Mad3 and Bub1 are necessary and
sufficient for interaction with Bub3. The calorimetrically determined
dissociation constants for GLEBS-motif peptides and Bub3 are approximately 5
microM. Crystal structures of these peptides with Bub3 show that the
interactions for Mad3 and Bub1 are similar and mutually exclusive. In both
structures, the GLEBS peptide snakes along the top surface of the
beta-propeller, forming an extensive interface. Mutations in either protein that
disrupt the interface cause checkpoint deficiency and chromosome instability. We
propose that the structure imposed on the GLEBS segment by its association with
Bub3 enables recruitment to unattached kinetochores.
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Figure 2.
Fig. 2. Negative-stain electron microscopy. Shown are wide
fields with higher magnification insets. (A) Bub3 appears as
isolated punctate objects. (B) Mad3 resembles elongated beads on
a string.
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Figure 5.
Fig. 5. Mad3 and R197E Bub3 do not associate. (A) Mad3 was
mixed with excess Bub3 mutant and analyzed by gel filtration.
(B) Coomassie-stained gel of peak fractions from A showing that
the Bub3 mutant does not coelute with Mad3.
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Secondary reference #1
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Title
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Crystal structure of the spindle assembly checkpoint protein bub3.
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Authors
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N.A.Larsen,
S.C.Harrison.
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Ref.
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J Mol Biol, 2004,
344,
885-892.
[DOI no: ]
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PubMed id
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Figure 1.
Figure 1. Annotated structural sequence alignment of Bub3.
The primary sequence of bakers yeast (SC) was aligned with known
bub3 homologs from Drosophila (DM), Xenopus (XL), mouse (MM),
and Human (HS) using CLUSTALW.^44 Residues in the sequence are
color coded according to their similarity. The coloring scheme
of the annotated secondary structure will be followed in
subsequent Figures. Highlighted residues correspond to the WD
signature sequence, which in Bub3p is highly divergent. The
residues in the conserved structural triad in blade 6 are also
highlighted.
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Figure 2.
Figure 2. Top/side views of Bub3. (A) The top view shows the
overall topology. Note that any given sequence repeat spans two
blades, forming βD in blade “n−1” and βA–βC in blade
“n”. The three Se-methionine residues (sticks) are shown.
Stars indicate disordered loop regions that were not traceable.
(B) A 90° rotation relative to the top view, illustrating
the relative height of the DA loop between blades 5 and 6 as
well as the BC loop in blade 7. The Figure was generated in
Bobscript^45 and rendered with Raster3d.^46
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The above figures are
reproduced from the cited reference
with permission from Elsevier
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