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PDBsum entry 1ixa
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Human factor ix
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PDB id
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1ixa
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References listed in PDB file
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Key reference
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Title
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The three-Dimensional structure of the first egf-Like module of human factor IX: comparison with egf and tgf-Alpha.
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Authors
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M.Baron,
D.G.Norman,
T.S.Harvey,
P.A.Handford,
M.Mayhew,
A.G.Tse,
G.G.Brownlee,
I.D.Campbell.
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Ref.
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Protein Sci, 1992,
1,
81-90.
[DOI no: ]
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PubMed id
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Abstract
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The three-dimensional structure of the first epidermal growth factor (EGF)-like
module from human factor IX has been determined in solution using
two-dimensional nuclear magnetic resonance (in the absence of calcium and at pH
4.5). The structure was found to resemble closely that of EGF and the homologous
transforming growth factor-alpha (TGF-alpha). Residues 60-65 form an
antiparallel beta-sheet with residues 68-73. In the C-terminal subdomain a type
II beta-turn is found between residues 74 and 77 and a five-residue turn is
found between residues 79 and 83. Glu 78 and Leu 84 pair in an antiparallel
beta-sheet conformation. In the N-terminal region a loop is found between
residues 50 and 55 such that the side chains of both are positioned above the
face of the beta-sheet. Residues 56-60 form a turn that leads into the first
strand of the beta-sheet. Whereas the global fold closely resembles that of EGF,
the N-terminal residues of the module (46-49) do not form a beta-strand but are
ill-defined in the structure, probably due to the local flexibility of this
region. The structure is discussed with reference to recent site-directed
mutagenesis data, which have identified certain conserved residues as ligands
for calcium.
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Figure 2.
Fig. 2. Experimentalrestraints. A: Experimentaldata used to identifysecondarystructure. Black boxesrepresentHN,HN<,,i-,,
andHN,Ha(,,,-,,NOEs.Theheightoftheboxrelatestothe size oftheNOE(strong,medium,weak).Openboxesrepresent
NOEs romprolineH6protons. S ndicatesresidueswhosebackboeaideprotonswere slow to xchange in D20, ad * in-
icates 3JHN ouplingconstantsgreaterthan 9 Hz. B: Thedistribution f long-range andshort-rangedistancerestraints.
barsrepresentlong-rangedistancerestraints(>i - [i + 1); openbarsrepresentshort-rangedistancerestraints(
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Figure 3.
Fig. 3. Distribution of NOE restraint energy forstructures produced
by restrained simulated annealing (i.e., prior o final minimization). Re-
straint energies are in kJ/mol; selection cutoff at 369 kJ/mol, denoted
by a
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The above figures are
reprinted
from an Open Access publication published by the Protein Society:
Protein Sci
(1992,
1,
81-90)
copyright 1992.
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