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PDBsum entry 1cu1
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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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Molecular views of viral polyprotein processing revealed by the crystal structure of the hepatitis c virus bifunctional protease-Helicase.
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Authors
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N.Yao,
P.Reichert,
S.S.Taremi,
W.W.Prosise,
P.C.Weber.
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Ref.
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Structure, 1999,
7,
1353-1363.
[DOI no: ]
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PubMed id
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Abstract
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BACKGROUND: Hepatitis C virus (HCV) currently infects approximately 3% of the
world's population. HCV RNA is translated into a polyprotein that during
maturation is cleaved into functional components. One component, nonstructural
protein 3 (NS3), is a 631-residue bifunctional enzyme with protease and helicase
activities. The NS3 serine protease processes the HCV polyprotein by both cis
and trans mechanisms. The structural aspects of cis processing, the
autoproteolysis step whereby the protease releases itself from the polyprotein,
have not been characterized. The structural basis for inclusion of protease and
helicase activities in a single polypeptide is also unknown. RESULTS: We report
here the 2.5 A resolution structure of an engineered molecule containing the
complete NS3 sequence and the protease activation domain of nonstructural
protein 4A (NS4A) in a single polypeptide chain (single chain or scNS3-NS4A). In
the molecule, the helicase and protease domains are segregated and connected by
a single strand. The helicase necleoside triphosphate and RNA interaction sites
are exposed to solvent. The protease active site of scNS3-NS4A is occupied by
the NS3 C terminus, which is part of the helicase domain. Thus, the
intramolecular complex shows one product of NS3-mediated cleavage at the
NS3-NS4A junction of the HCV polyprotein bound at the protease active site.
CONCLUSIONS: The scNS3-NS4A structure provides the first atomic view of
polyprotein cis processing. Both local and global structural rearrangements
follow the cis cleavage reaction, and large segments of the polyprotein can be
folded prior to proteolytic processing. That the product complex of the cis
cleavage reaction exists in a stable molecular conformation suggests
autoinhibition and substrate-induced activation mechanisms for regulation of NS3
protease activity.
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Figure 8.
Figure 8. HCV polyprotein processing in the nonstructural
region. Nonstructural proteins NS3, NS4A, NS4B, NS5A and NS5B
are colored purple, red, green, pink and orange, respectively.
(a) Attachment of the 1984-residue polyprotein to the membrane.
(b) NS4A activation and folding of the NS3 N terminus. (c)
Subsequent cleavage reactions. To highlight the fact that the
sequence of cleavage reactions has not been firmly established,
the N terminus of the polyprotein substrate is dotted and the
schematic diagrams are enclosed in a box. (d) The release of
NS4B and NS5A and formation of the replication complex core.
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The above figure is
reprinted
by permission from Cell Press:
Structure
(1999,
7,
1353-1363)
copyright 1999.
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