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PDBsum entry 1z1i
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References listed in PDB file
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Key reference
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Title
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Mechanism of the maturation process of sars-Cov 3cl protease.
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Authors
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M.F.Hsu,
C.J.Kuo,
K.T.Chang,
H.C.Chang,
C.C.Chou,
T.P.Ko,
H.L.Shr,
G.G.Chang,
A.H.Wang,
P.H.Liang.
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Ref.
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J Biol Chem, 2005,
280,
31257-31266.
[DOI no: ]
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PubMed id
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Abstract
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Severe acute respiratory syndrome (SARS) is an emerging infectious disease
caused by a novel human coronavirus. Viral maturation requires a main protease
(3CL(pro)) to cleave the virus-encoded polyproteins. We report here that the
3CL(pro) containing additional N- and/or C-terminal segments of the polyprotein
sequences undergoes autoprocessing and yields the mature protease in vitro. The
dimeric three-dimensional structure of the C145A mutant protease shows that the
active site of one protomer binds with the C-terminal six amino acids of the
protomer from another asymmetric unit, mimicking the product-bound form and
suggesting a possible mechanism for maturation. The P1 pocket of the active site
binds the Gln side chain specifically, and the P2 and P4 sites are clustered
together to accommodate large hydrophobic side chains. The tagged C145A mutant
protein served as a substrate for the wild-type protease, and the N terminus was
first digested (55-fold faster) at the Gln(-1)-Ser1 site followed by the
C-terminal cleavage at the Gln306-Gly307 site. Analytical ultracentrifuge of the
quaternary structures of the tagged and mature proteases reveals the remarkably
tighter dimer formation for the mature enzyme (K(d) = 0.35 nm) than for the
mutant (C145A) containing 10 extra N-terminal (K(d) = 17.2 nM) or C-terminal
amino acids (K(d) = 5.6 nM). The data indicate that immature 3CL(pro) can form
dimer enabling it to undergo autoprocessing to yield the mature enzyme, which
further serves as a seed for facilitated maturation. Taken together, this study
provides insights into the maturation process of the SARS 3CL(pro) from the
polyprotein and design of new structure-based inhibitors.
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Figure 5.
FIG. 5. Molecular interactions of the active site residues
of protomer B with the C-terminal residues of protomer B'. A,
stereo view of the electron density map of the C-terminal region
(red stick) of protomer B' bound in the S pockets (cyan stick)
of protomer B. B, details of the molecular interactions between
the active site S1-S6 pockets of protomer B and the C-terminal
residues of protomer B'. H-bonds are shown as green broken lines.
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Figure 6.
FIG. 6. Superposition of 3CLpro active sites and
inhibitors. A, superimposition of the active site of five 3CLpro
protease structures: cyan and blue, protomer A and B of C145A;
light green and gold, protomer A and B of the wild type,
respectively; crimson, HCoV 229E 3CLpro (1P9S); and pink, TGEV
3CLpro (1P9U). B, superimposition of the six C-terminal residues
of SARS 3CLpro (SGVTFQ) (cyan), the inhibitor of TGEV 3CLpro
(1P9U, pink), the inhibitor of TGEV 3CLpro (VNSTLQ) at the
active site of SARS 3CLpro (1UK4, gold), and the inhibitor of
Rhinovirus 3CLpro, AG7088 at the active site (1CQQ, green).
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The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(2005,
280,
31257-31266)
copyright 2005.
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