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PDBsum entry 2qpf
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Transport protein
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PDB id
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2qpf
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References listed in PDB file
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Key reference
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Title
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Human-Murine transthyretin heterotetramers are kinetically stable and non-Amyloidogenic: a lesson in the generation of transgenic models of diseases involving oligomeric proteins.
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Authors
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N.Reixach,
T.R.Foss,
E.Santelli,
J.Pascual,
J.W.Kelly,
J.N.Buxbaum.
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Ref.
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J Biol Chem, 2008,
283,
2098-2107.
[DOI no: ]
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PubMed id
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Abstract
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The transthyretin amyloidoses appear to be caused by rate-limiting tetramer
dissociation and partial monomer unfolding of the human serum protein
transthyretin, resulting in aggregation and extracellular deposition of
amorphous aggregates and amyloid fibrils. Mice transgenic for few copies of
amyloid-prone human transthyretin variants, including the aggressive L55P
mutant, failed to develop deposits. Silencing the murine transthyretin gene in
the presence of the L55P human gene resulted in enhanced tissue deposition. To
test the hypothesis that the murine protein interacted with human transthyretin,
preventing the dissociation and partial unfolding required for amyloidogenesis,
we produced recombinant murine transthyretin and human/murine transthyretin
heterotetramers and compared their structures and biophysical properties to
recombinant human transthyretin. We found no significant differences between the
crystal structures of murine and human homotetramers. Murine transthyretin is
not amyloidogenic because the native homotetramer is kinetically stable under
physiologic conditions and cannot dissociate into partially unfolded monomers,
the misfolding and aggregation precursor. Heterotetramers composed of murine and
human subunits are also kinetically stable. These observations explain the lack
of transthyretin deposition in transgenics carrying a low copy number of human
transthyretin genes. The incorporation of mouse subunits into tetramers
otherwise composed of human amyloid-prone transthyretin subunits imposes kinetic
stability, preventing dissociation and subsequent amyloidogenesis.
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Figure 1.
FIGURE 1. A, primary structure alignment of Hu-TTR and
Mu-TTR. Stars at the bottom indicate identical amino acid
residues. B, two views of the crystal structure of Mu-TTR
superimposed on that of Hu-TTR. Each mouse TTR subunit is shown
in a different color; Hu-TTR is shown in gray. Dashed lines
indicate the dimer interfaces, and the crystallographic C[2] x
axis is labeled.
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Figure 4.
FIGURE 4. Kinetics of tetramer disassembly (closed symbols)
and unfolding (open symbols) in 6 M urea for Hu-TTR (triangles)
and Mu-TTR (circles). For both Hu-TTR and Mu-TTR the loss of
quaternary structure (disassembly) and the loss of tertiary
structure (unfolding) are tightly linked. Mu-TTR is kinetically
stabilized compared with Hu-TTR as seen by its significantly
slower dissociation/unfolding kinetics. Tetramer disassembly was
measured by resveratrol binding fluorescence; unfolding was
measured by tryptophan fluorescence.
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The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(2008,
283,
2098-2107)
copyright 2008.
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