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PDBsum entry 1u2h
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Contractile protein
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PDB id
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1u2h
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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 structure of engineered human aortic preferentially expressed protein-1 (apeg-1).
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Authors
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B.A.Manjasetty,
F.H.Niesen,
C.Scheich,
Y.Roske,
F.Goetz,
J.Behlke,
V.Sievert,
U.Heinemann,
K.Büssow.
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Ref.
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Bmc Struct Biol, 2005,
5,
21.
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PubMed id
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Abstract
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BACKGROUND: Human Aortic Preferentially Expressed Protein-1 (APEG-1) is a novel
specific smooth muscle differentiation marker thought to play a role in the
growth and differentiation of arterial smooth muscle cells (SMCs). RESULTS: Good
quality crystals that were suitable for X-ray crystallographic studies were
obtained following the truncation of the 14 N-terminal amino acids of APEG-1, a
region predicted to be disordered. The truncated protein (termed DeltaAPEG-1)
consists of a single immunoglobulin (Ig) like domain which includes an
Arg-Gly-Asp (RGD) adhesion recognition motif. The RGD motif is crucial for the
interaction of extracellular proteins and plays a role in cell adhesion. The
X-ray structure of DeltaAPEG-1 was determined and was refined to sub-atomic
resolution (0.96 A). This is the best resolution for an immunoglobulin domain
structure so far. The structure adopts a Greek-key beta-sandwich fold and
belongs to the I (intermediate) set of the immunoglobulin superfamily. The
residues lying between the beta-sheets form a hydrophobic core. The RGD motif
folds into a 310 helix that is involved in the formation of a homodimer in the
crystal which is mainly stabilized by salt bridges. Analytical
ultracentrifugation studies revealed a moderate dissociation constant of 20
microM at physiological ionic strength, suggesting that APEG-1 dimerisation is
only transient in the cell. The binding constant is strongly dependent on ionic
strength. CONCLUSION: Our data suggests that the RGD motif might play a role not
only in the adhesion of extracellular proteins but also in intracellular
protein-protein interactions. However, it remains to be established whether the
rather weak dimerisation of APEG-1 involving this motif is physiologically
relevant.
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