Figure 2.
Figure 2: Key aspects of various phi-6
polymerase structures. a, 6
polymerase sliced open; arrows highlight key features. The areas
of the surrounding close-ups in b-e are marked by
semitransparent boxes, and orientations shown are with respect
to a. b, Surface representation28 viewed from above showing the
entrance to the template tunnel. Putative positions for the
strands before initiation are shown. c, A section through the
template channel with the bound oligomer drawn in yellow. The
surface of the polymerase and the embedded polypeptide chain are
coloured green. The two 3' cytidines are marked as T1 and T2. d,
Difference electron density map for the NTP bound to site I
(based on ninefold averaging of three difference density maps).
ATP is drawn with the phosphates coloured green. e, Stereo image
of the initiation complex. The 3' cytidines (T1 & T2) are drawn
in blue. The incoming GTPs, D1 and D2, are shown base paired
(bonds in red) to T1 and T2. Y630 ring stacks with the base of
D1. D453, D454 and D324 are the catalytic aspartates, the Mn2+
ion is shown in cyan, the two catalytic Mg2+ ions are in green.
The above figure is reprinted
by permission from Macmillan Publishers Ltd:
Nature
(2001,
410,
235-240)
copyright 2001.
6
polymerase structures. a, 
6
polymerase sliced open; arrows highlight key features. The areas
of the surrounding close-ups in b-e are marked by
semitransparent boxes, and orientations shown are with respect
to a. b, Surface representation28 viewed from above showing the
entrance to the template tunnel. Putative positions for the
strands before initiation are shown. c, A section through the
template channel with the bound oligomer drawn in yellow. The
surface of the polymerase and the embedded polypeptide chain are
coloured green. The two 3' cytidines are marked as T1 and T2. d,
Difference electron density map for the NTP bound to site I
(based on ninefold averaging of three difference density maps).
ATP is drawn with the phosphates coloured green. e, Stereo image
of the initiation complex. The 3' cytidines (T1 & T2) are drawn
in blue. The incoming GTPs, D1 and D2, are shown base paired
(bonds in red) to T1 and T2. Y630 ring stacks with the base of
D1. D453, D454 and D324 are the catalytic aspartates, the Mn2+
ion is shown in cyan, the two catalytic Mg2+ ions are in green.