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PDBsum entry 2r6e
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References listed in PDB file
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Key reference
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Title
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Structure of hexameric dnab helicase and its complex with a domain of dnag primase.
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Authors
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S.Bailey,
W.K.Eliason,
T.A.Steitz.
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Ref.
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Science, 2007,
318,
459-463.
[DOI no: ]
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PubMed id
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Abstract
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The complex between the DnaB helicase and the DnaG primase unwinds duplex DNA at
the eubacterial replication fork and synthesizes the Okazaki RNA primers. The
crystal structures of hexameric DnaB and its complex with the helicase binding
domain (HBD) of DnaG reveal that within the hexamer the two domains of DnaB pack
with strikingly different symmetries to form a distinct two-layered ring
structure. Each of three bound HBDs stabilizes the DnaB hexamer in a
conformation that may increase its processivity. Three positive, conserved
electrostatic patches on the N-terminal domain of DnaB may also serve as a
binding site for DNA and thereby guide the DNA to a DnaG active site.
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Figure 1.
Fig. 1. Architecture of the DnaB hexamer. (A) Experimentally
phased and cross-crystal averaged electron density maps of the
four DnaB crystal forms. Shown at the foot of each map is the
high-resolution limit at which each map was calculated. (B)
"Side" view, orthogonal to the ring axis, of a ribbon
representation of the DnaB hexamer. The NTD, CTD, and linker
region are colored blue, red, and yellow respectively. (C) "Top"
view, looking down the ring axis, of the DnaB hexamer. The CTDs
are shown in a surface representation; the NTDs are shown as
ribbons. Those subunits whose NTDs lie on the inner surface of
the ring are colored as in (B), and those on the outer surface
of the ring are colored white. (D) "Side" view of the two
distinct conformations of the DnaB subunits within the hexamer,
colored as in (B). Adjacent CTDs interacting with the linker
region are shown as white surface representations.
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Figure 3.
Fig. 3. Structure of the complex between DnaB and HBD. (A)
(Top) "Top" view of a ribbon representation of the complex
showing the three HBDs (green) bound at the periphery of the NTD
collar (light blue and blue). The CTD and linker region are
colored red and yellow, respectively. (Bottom) The interface
between DnaB and HBD shown as ribbons with a transparent
surface. (B) "Side" view of a surface representation of the
complex revealing no interaction between the HBDs (green) and
the DnaB CTD (red) or linker region (yellow). (C) Backbone trace
of the HBD DnaB interface, residues known to modulate the
interaction between DnaB and DnaG, are shown as colored spheres.
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The above figures are
reprinted
by permission from the AAAs:
Science
(2007,
318,
459-463)
copyright 2007.
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