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PDBsum entry 1u4q
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Structural protein
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PDB id
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1u4q
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References listed in PDB file
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Key reference
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Title
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Independent movement, Dimerization and stability of tandem repeats of chicken brain alpha-Spectrin.
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Authors
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H.Kusunoki,
G.Minasov,
R.I.Macdonald,
A.Mondragón.
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Ref.
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J Mol Biol, 2004,
344,
495-511.
[DOI no: ]
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PubMed id
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Abstract
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Previous X-ray crystal structures have shown that linkers of five amino acid
residues connecting pairs of chicken brain alpha-spectrin and human erythroid
beta-spectrin repeats can undergo bending without losing their alpha-helical
structure. To test whether bending at one linker can influence bending at an
adjacent linker, the structures of two and three repeat fragments of chicken
brain alpha-spectrin have been determined by X-ray crystallography. The
structure of the three-repeat fragment clearly shows that bending at one linker
can occur independently of bending at an adjacent linker. This observation
increases the possible trajectories of modeled chains of spectrin repeats.
Furthermore, the three-repeat molecule crystallized as an antiparallel dimer
with a significantly smaller buried interfacial area than that of alpha-actinin,
a spectrin-related molecule, but large enough and of a type indicating
biological specificity. Comparison of the structures of the spectrin and
alpha-actinin dimers supports weak association of the former, which could not be
detected by analytical ultracentrifugation, versus strong association of the
latter, which has been observed by others. To correlate features of the
structure with solution properties and to test a previous model of stable
spectrin and dystrophin repeats, the number of inter-helical interactions in
each repeat of several spectrin structures were counted and compared to their
thermal stabilities. Inter-helical interactions, but not all interactions,
increased in parallel with measured thermal stabilities of each repeat and in
agreement with the thermal stabilities of two and three repeats and also partial
repeats of spectrin.
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Figure 1.
Figure 1. Electron density maps of linker regions of
CBa15-17. Stereo views of the final 2F[o] -F[c] maps around the
linker region between R15 and R16 (top panel) and between R16
and R17 (bottom panel) at 2.5 Å resolution. The maps are
contoured at the 1.0 s level and shown by a blue mesh. The final
models of the linker regions are shown with a color scheme
identical with that in Figure 2.
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Figure 4.
Figure 4. CBa15-17 dimer. A, Ribbon diagrams of the
CBa15-17 dimer (left panel) and a-actinin dimer (right panel)
are shown. In CBa15-17, R15 (residues 1665-1770) is shown in
orange, R16 (residues 1771-1876) in yellow, and R17 (residues
1877-1981) in green. Residues 1662-1664 in molecule A are shown
in white. In a-actinin, R1 (residues 274-393) is shown in white,
R2 (residues 394-508) in pink, R3 (residues 509-633) in magenta,
and R4 (residues 634-746) in blue. Residues 272 and 273 are
shown in brown. B, Space-filling models of the CBa15-17 dimer
(left panel) and a-actinin dimer (right panel) are shown. The
color scheme is identical with that in A. The lines were drawn
to delineate the boundaries of repeat pairs.
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The above figures are
reprinted
by permission from Elsevier:
J Mol Biol
(2004,
344,
495-511)
copyright 2004.
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