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Figure 3.
Figure 3. Crown-Shaped Appearance of the T7
Primase-HelicaseA side view of the surface of the
primase-helicase shows that the primase domains (top of figure)
are swapped onto neighboring helicase domains (bottom), which
pack together in a closed ring. An extended “clasp” between
the primase and helicase domains packs against the adjacent
subunit and contributes most of the contacts between subunits
(cf. Figure 4). The primase domains make few contacts with one
another and they are oriented differently in all seven subunits
(cf. Figure 1). This loose-packed arrangement would allow a DNA
template to bind to the primase active site in the gap between
adjacent primase domains. The surface rendering was generated
with the program MOLMOL (Koradi et al., 1996) and rendered with
POV-Ray (Amundsen et al., 2000).
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