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PDBsum entry 2lv6
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Metal binding protein/transferase
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PDB id
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2lv6
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References listed in PDB file
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Key reference
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Title
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Contrast-Matched small-Angle X-Ray scattering from a heavy-Atom-Labeled protein in structure determination: application to a lead-Substituted calmodulin-Peptide complex.
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Authors
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A.Grishaev,
N.J.Anthis,
G.M.Clore.
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Ref.
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J Am Chem Soc, 2012,
134,
14686-14689.
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PubMed id
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Abstract
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The information content in 1-D solution X-ray scattering profiles is generally
restricted to low-resolution shape and size information that, on its own, cannot
lead to unique 3-D structures of biological macromolecules comparable to
all-atom models derived from X-ray crystallography or NMR spectroscopy. Here we
show that contrast-matched X-ray scattering data collected on a protein
incorporating specific heavy-atom labels in 65% aqueous sucrose buffer can
dramatically enhance the power of conventional small- and wide-angle X-ray
scattering (SAXS/WAXS) measurements. Under contrast-matching conditions the
protein is effectively invisible and the main contribution to the X-ray
scattering intensity arises from the heavy atoms, allowing direct extraction of
pairwise distances between them. In combination with conventional aqueous
SAXS/WAXS data, supplemented by NMR-derived residual dipolar couplings (RDCs)
measured in a weakly aligning medium, we show that it is possible to position
protein domains relative to one another within a precision of 1 Å. We
demonstrate this approach with respect to the determination of domain positions
in a complex between calmodulin, in which the four Ca(2+) ions have been
substituted by Pb(2+), and a target peptide. The uniqueness of the resulting
solution is established by an exhaustive search over all models compatible with
the experimental data, and could not have been achieved using aqueous SAXS and
RDC data alone. Moreover, we show that the correct structural solution can be
recovered using only contrast-matched SAXS and aqueous SAXS/WAXS data.
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