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Title
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Refined structure of Sindbis virus core protein and comparison with other chymotrypsin-like serine proteinase structures.
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Authors
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L.Tong,
G.Wengler,
M.G.Rossmann.
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Ref.
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J Mol Biol, 1993,
230,
228-247.
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PubMed id
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Abstract
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Crystal forms 2 and 3 of Sindbis virus core protein have been refined to 2.8 A
and 3.0 A resolution, respectively. The three independent molecular copies in
the two crystal forms are essentially identical, except for regions where the
molecules are involved in different crystal packing interactions. The overall
polypeptide backbone fold of Sindbis virus core protein is similar to other
chymotrypsin-like serine proteinase structures despite a lack of significant
sequence homology. Detailed analysis revealed differences in the catalytic triad
and the substrate binding pockets between the Sindbis virus core protein and the
other serine proteinases. The catalytic aspartic acid residue (Asp163) and
residue Asp214 (corresponding to Asp194 in chymotrypsin) are partially exposed
to solvent in Sindbis virus core protein. Chymotrypsin Ser214, hydrogen bonded
to the catalytic aspartic acid residue in all other serine proteinase
structures, is changed to Leu231 in Sindbis virus core protein. Deletions in the
loop regions on the surface of the protein account for the smaller size of the
ordered part of Sindbis virus core protein (151 residues) as compared to
chymotrypsin (236 residues), and permits the cis autocatalytic cleavage of the
polyprotein to produce the viral capsid protein.
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