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Title
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Structure of ubiquitin refined at 1.8 A resolution.
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Authors
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S.Vijay-Kumar,
C.E.Bugg,
W.J.Cook.
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Ref.
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J Mol Biol, 1987,
194,
531-544.
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PubMed id
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Abstract
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The crystal structure of human erythrocytic ubiquitin has been refined at 1.8 A
resolution using a restrained least-squares procedure. The crystallographic
R-factor for the final model is 0.176. Bond lengths and bond angles in the
molecule have root-mean-square deviations from ideal values of 0.016 A and 1.5
degrees, respectively. A total of 58 water molecules per molecule of ubiquitin
are included in the final model. The last four residues in the molecule appear
to have partial occupancy or large thermal motion. The overall structure of
ubiquitin is extremely compact and tightly hydrogen-bonded; approximately 87% of
the polypeptide chain is involved in hydrogen-bonded secondary structure.
Prominent secondary structural features include three and one-half turns of
alpha-helix, a short piece of 3(10)-helix, a mixed beta-sheet that contains five
strands, and seven reverse turns. There is a marked hydrophobic core formed
between the beta-sheet and alpha-helix. The molecule features a number of
unusual secondary structural features, including a parallel G1 beta-bulge, two
reverse Asx turns, and a symmetrical hydrogen-bonding region that involves the
two helices and two of the reverse turns.
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