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PDBsum entry 1sw6
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Transcription regulation
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PDB id
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1sw6
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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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X-Ray structural analysis of the yeast cell cycle regulator swi6 reveals variations of the ankyrin fold and has implications for swi6 function.
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Authors
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R.Foord,
I.A.Taylor,
S.G.Sedgwick,
S.J.Smerdon.
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Ref.
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Nat Struct Biol, 1999,
6,
157-165.
[DOI no: ]
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PubMed id
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Abstract
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Swi6 is a 92,000 Mr protein common to two distinct transcriptional activation
complexes (SBF and MBF) that coordinate gene expression at the G1-S boundary of
the yeast cell cycle. The X-ray structure of a central 36,000 Mr fragment has
been determined and refined at 2.1 A resolution. The structure reveals a basic
framework of five ankyrin repeat modules that is elaborated through a series of
helical insertions distinguishing it from structures of other ankyrin repeat
proteins. A second domain contains an approximately 30-residue region of
extended structure that interacts with the ankyrin repeat core over a
substantial proportion of its surface. Conservation of residues buried by these
interactions indicates that all members of the Swi6/Cdc10 family share a similar
architecture. Several temperature-sensitive mutations within Swi6 and Cdc10
appear to disrupt these interdomain contacts rather than destabilize the ankyrin
repeat core. The unusual domain arrangement may be crucial for the modulation of
interactions with other co-regulatory molecules such as cyclin-CDK complexes,
and has implications for the quaternary interactions within the multisubunit SBF
and MBF transcription complexes.
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Figure 1.
Figure 1. a, Schematic representation of the protein components
and DNA−binding specificity of the SBF and MBF complexes.
b, Regions of sequence homology within the Swi6/Cdc10 family.
The leucine heptad repeat, present only in Swi6 and Cdc10, is
indicated, together with the boundaries of the Swi6 fragment
(Swi6−36kD) used in this study.
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Figure 5.
Figure 5. a, Contacts between the AAD and the upper surface of
the ANK core. The AAD is shown as a coil with side chains
attached. The molecular surface of the ANK is colored white, and
the surface associated with atoms within van der Waals contact
of the AAD is colored red. b, Residues within the first ANK
repeat of Swi6 (left) generate an extensive hydrophobic surface
(red) that is partially occluded through interactions with the
AAD (shown as blue coil). Mapping sequence substitutions in Swi4
(right) and Mbp1 (not shown) onto the Swi6 backbone structure
shows that this surface is conserved and suggests that a similar
AAD−like structure is likely to be present in these and the
other Swi6−related proteins. The surface associated with the
conserved Swi6 Trp 344 is colored blue. Parts (a) and (b)
produced using GRASP^61. c, Homology within the region
immediately N−terminal to the ANK core of Swi6/Cdc10−related
proteins. The homologous cluster of nonpolar residues and the
N−terminal segment of the first ANK repeat are boxed. Figs 4
and 5c produced using ALSCRIPT^62.
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The above figures are
reprinted
by permission from Macmillan Publishers Ltd:
Nat Struct Biol
(1999,
6,
157-165)
copyright 1999.
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