D. Tok Pol
Yanxiang Zhao, David Jeruzalmi, Ismail Moarefi, Lore Leighton,
Roger Lasken, John Kuriyan
Members of the Pol II family of DNA polymerases are responsible
for chromosomal replication in eukaryotes, and carry out highly
processive DNA replication when attached to ring-shaped processivity
clamps. The DNA polymerase from the archaebacterium Desulfurococcus
strain Tok (D. Tok Pol) is a member of the Pol II family that
retains catalytic activity at elevated temperatures. In the crystal
structure, the central catalytic region of the DNA polymerase
is located within the 'palm' subdomain and is strikingly similar
in structure to the corresponding regions of Pol I type DNA polymerases.
The structural scaffold that surrounds the catalytic core in D.
Tok Pol is unrelated in structure to that of Pol I type polymerases.
The structure of D. Tok Pol confirms that the modes of binding
of the template and extrusion of newly synthesized duplex DNA
are likely to be similar in both Pol II and Pol I type DNA polymerases.
However, the mechanism by which the newly synthesized product
transits in and out of the proofreading exonuclease domain has
to be quite different. The N-terminal domain of D. Tok Pol has
structural similarity to RNA-binding domains. Sequence alignments
suggest that this domain is conserved in the eukaryotic DNA polymerases
delta and epsilon, raising the possibility that Pol II family
members interact with RNA.
Protein Structure Coordinates
(PDB Entry Number 1QQC)
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