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PDBsum entry 1cdc
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Immune system protein, receptor
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PDB id
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1cdc
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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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One sequence, Two folds: a metastable structure of cd2.
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Authors
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A.J.Murray,
S.J.Lewis,
A.N.Barclay,
R.L.Brady.
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Ref.
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Proc Natl Acad Sci U S A, 1995,
92,
7337-7341.
[DOI no: ]
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PubMed id
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Note In the PDB file this reference is
annotated as "TO BE PUBLISHED".
The citation details given above were identified by an automated
search of PubMed on title and author
names, giving a
perfect match.
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Abstract
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When expressed as part of a glutathione S-transferase fusion protein the
NH2-terminal domain of the lymphocyte cell adhesion molecule CD2 is shown to
adopt two different folds. The immunoglobulin superfamily structure of the major
(85%) monomeric component has previously been determined by both x-ray
crystallography and NMR spectroscopy. We now describe the structure of a second,
dimeric, form present in about 15% of recombinant CD2 molecules. After
denaturation and refolding in the absence of the fusion partner, dimeric CD2 is
converted to monomer, illustrating that the dimeric form represents a metastable
folded state. The crystal structure of this dimeric form, refined to 2.0-A
resolution, reveals two domains with overall similarity to the IgSF fold found
in the monomer. However, in the dimer each domain is formed by the intercalation
of two polypeptide chains. Hence each domain represents a distinct folding unit
that can assemble in two different ways. In the dimer the two domains fold
around a hydrophilic interface believed to mimic the cell adhesion interaction
at the cell surface, and the formation of dimer can be regulated by mutating
single residues at this interface. This unusual misfolded form of the protein,
which appears to result from inter- rather than intramolecular interactions
being favored by an intermediate structure formed during the folding process,
illustrates that evolution of protein oligomers is possible from the sequence
for a single protein domain.
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