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Title
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Crystal structure of Thermus aquaticus DNA polymerase.
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Authors
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Y.Kim,
S.H.Eom,
J.Wang,
D.S.Lee,
S.W.Suh,
T.A.Steitz.
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Ref.
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Nature, 1995,
376,
612-616.
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PubMed id
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Abstract
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The DNA polymerase from Thermus aquaticus (Taq polymerase), famous for its use
in the polymerase chain reaction, is homologous to Escherichia coli DNA
polymerase I (pol I) Like pol I, Taq polymerase has a domain at its amino
terminus (residues 1-290) that has 5' nuclease activity and a domain at its
carboxy terminus that catalyses the polymerase reaction. Unlike pol I, the
intervening domain in Taq polymerase has lost the editing 3'-5' exonuclease
activity. Although the structure of the Klenow fragment of pol I has been known
for ten years, that of the intact pol I has proved more elusive. The structure
of Taq polymerase determined here at 2.4 A resolution shows that the structures
of the polymerase domains of the thermostable enzyme and of the Klenow fragment
are nearly identical, whereas the catalytically critical carboxylate residues
that bind two metal ions are missing from the remnants of the 3'-5' exonuclease
active site of Taq polymerase. The first view of the 5' nuclease domain,
responsible for excising the Okazaki RNA in lagging-strand DNA replication,
shows a cluster of conserved divalent metal-ion-binding carboxylates at the
bottom of a cleft. The location of this 5'-nuclease active site some 70 A from
the polymerase active site in this crystal form highlights the unanswered
question of how this domain works in concert with the polymerase domain to
produce a duplex DNA product that contains only a nick.
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