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PDBsum entry 2p6u
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DNA binding protein
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PDB id
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2p6u
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References listed in PDB file
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Key reference
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Title
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Structural basis for DNA duplex separation by a superfamily-2 helicase.
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Authors
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K.Büttner,
S.Nehring,
K.P.Hopfner.
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Ref.
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Nat Struct Biol, 2007,
14,
647-652.
[DOI no: ]
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PubMed id
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Abstract
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To reveal the mechanism of processive strand separation by superfamily-2 (SF2)
3'-->5' helicases, we determined apo and DNA-bound crystal structures of
archaeal Hel308, a helicase that unwinds lagging strands and is related to human
DNA polymerase theta. Our structure captures the duplex-unwinding reaction,
shows that initial strand separation does not require ATP and identifies a
prominent beta-hairpin loop as the unwinding element. Similar loops in hepatitis
C virus NS3 helicase and RNA-decay factors support the idea that this
duplex-unwinding mechanism is applicable to a broad subset of SF2 helicases.
Comparison with ATP-bound SF2 enzymes suggests that ATP promotes processive
unwinding of 1 base pair by ratchet-like transport of the 3' product strand. Our
results provide a first structural framework for strand separation by processive
SF2 3'-->5' helicases and reveal important mechanistic differences from SF1
helicases.
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Figure 1.
(a) Schematic of the five domains of Hel308. Domain
boundaries are indicated on top, sequence motifs beneath. Roman
numerals, SF2 helicase motifs;  ,
-hairpin
loop; R, ratchet helix; RAR, Arg-Ala-Arg motif. (b) Hel308
(ribbon, colored as in a) in complex with the 15-base-pair DNA
duplex and 10-base single-stranded 3' tail (beige sticks). (c)
Schematic showing key interactions (dashed lines) of Hel308 with
the partially unwound DNA substrate.
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Figure 4.
Shown are products of proteolysis digestion of archaeal
Hel308 by indicated amounts of proteinase K in the presence or
absence of AMP-PNP and DNA.
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The above figures are
reprinted
by permission from Macmillan Publishers Ltd:
Nat Struct Biol
(2007,
14,
647-652)
copyright 2007.
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