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PDBsum entry 2ahm
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Viral protein, replication
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PDB id
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2ahm
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Contents |
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77 a.a.
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155 a.a.
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143 a.a.
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191 a.a.
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References listed in PDB file
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Key reference
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Title
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Insights into sars-Cov transcription and replication from the structure of the nsp7-Nsp8 hexadecamer.
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Authors
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Y.Zhai,
F.Sun,
X.Li,
H.Pang,
X.Xu,
M.Bartlam,
Z.Rao.
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Ref.
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Nat Struct Biol, 2005,
12,
980-986.
[DOI no: ]
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PubMed id
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Abstract
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Coronavirus replication and transcription machinery involves multiple
virus-encoded nonstructural proteins (nsp). We report the crystal structure of
the hexadecameric nsp7-nsp8 supercomplex from the severe acute respiratory
syndrome coronavirus at 2.4-angstroms resolution. nsp8 has a novel 'golf-club'
fold with two conformations. The supercomplex is a unique hollow, cylinder-like
structure assembled from eight copies of nsp8 and held tightly together by eight
copies of nsp7. With an internal diameter of approximately 30 angstroms, the
central channel has dimensions and positive electrostatic properties favorable
for nucleic acid binding, implying that its role is to confer processivity on
RNA-dependent RNA polymerase.
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Figure 3.
Figure 3. Architecture and assembly of the hexadecameric
nsp7–nsp8 complex. (a) The interaction sites between nsp7
and nsp8I/II. Green, nsp7; blue, nsp8. (b) T1 and T2
heterotetramer formation. The two dimers from one tetramer are
illustrated by the surface representation and ribbon diagram,
respectively. Residues: green, polar; yellow, hydrophobic; red,
acidic; blue, basic. Ribbons: green, nsp7; blue, nsp8I; orange,
nsp8II. (c) Possible pathway for assembly of the complex by
heterotetramers T1 and T2. (d) Hexadecameric supercomplex
construction with 'bricks' of nsp8 and 'mortar' of nsp7. The
angle between nsp8I and nsp8II is labeled in magenta. In c and
d, nsp7 molecules interacting with nsp8I and nsp8II are colored
yellow-green and blue-green, respectively.
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Figure 4.
Figure 4. Hypothetical interaction between RNA and the
hexadecameric nsp7–nsp8 complex. (a) The electrostatic
potential surface of the hexadecamer modeled with (right) and
without (left) duplex RNA in the positive channel. Blue,
positive charge (+10 k[B]T); red, negative charge (-10 k[B]T).
(b) Model of the hexadecameric nsp7–nsp8 supercomplex with
hypothetical duplex RNA. Left, top view, showing the channel's
proper dimensions to accommodate dsRNA. Right, side view,
showing a possible mode of interaction where the four nsp8II NH3
helices insert into the dsRNA grooves. (c,d) Results of EMSAs of
nsp7, nsp8 and their mutants. Each lane contains 75 pmol dsRNA
(c) or dsDNA (d). Lanes 1–7 contain 650 pmol of each protein;
lanes 8–13 contain 90 pmol of hexadecamer.
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The above figures are
reprinted
by permission from Macmillan Publishers Ltd:
Nat Struct Biol
(2005,
12,
980-986)
copyright 2005.
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