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PDBsum entry 1ce3
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Protease inhibitor
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PDB id
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1ce3
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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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Structure of a putative ancestral protein encoded by a single sequence repeat from a multidomain proteinase inhibitor gene from nicotiana alata.
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Authors
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M.J.Scanlon,
M.C.Lee,
M.A.Anderson,
D.J.Craik.
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Ref.
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Structure, 1999,
7,
793-802.
[DOI no: ]
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PubMed id
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Abstract
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BACKGROUND: The ornamental tobacco Nicotiana alata produces a series of
proteinase inhibitors (PIs) that are derived from a 43 kDa precursor protein,
NaProPI. NaProPI contains six highly homologous repeats that fold to generate
six separate structural domains, each corresponding to one of the native PIs. An
unusual feature of NaProPI is that the structural domains lie across adjacent
repeats and that the sixth PI domain is generated from fragments of the first
and sixth repeats. Although the homology of the repeats suggests that they may
have arisen from gene duplication, the observed folding does not appear to
support this. This study of the solution structure of a single NaProPI repeat
(aPI1) forms a basis for unravelling the mechanism by which this protein may
have evolved. RESULTS: The three-dimensional structure of aPI1 closely resembles
the triple-stranded antiparallel beta sheet observed in each of the native PIs.
The five-residue sequence Glu-Glu-Lys-Lys-Asn, which forms the linker between
the six structural domains in NaProPI, exists as a disordered loop in aPI1. The
presence of this loop in aPI1 results in a loss of the characteristically flat
and disc-like topography of the native inhibitors. CONCLUSIONS: A single repeat
from NaProPI is capable of folding into a compact globular domain that displays
native-like PI activity. Consequently, it is possible that a similar
single-domain inhibitor represents the ancestral protein from which NaProPI
evolved.
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Figure 4.
Figure 4. Schematic diagram of the secondary structural
elements of aPI1 showing the NOEs betweenβ strands
(double-headed arrows) and the position of proposed hydrogen
bonds (broken lines).
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The above figure is
reprinted
by permission from Cell Press:
Structure
(1999,
7,
793-802)
copyright 1999.
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