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Figure 2.
Figure 2. Filaments of Rad51 and RecA. (a) The Rad51 filament
found in these crystals has a helical pitch of 130 Å and is
composed of two crystallographically independent monomers
(yellow and green) that alternate to form a filament with exact
three-fold but only approximate six-fold screw symmetry. A
sulfate (black spheres) mimics the binding of phosphate in the
ATPase site, which is nestled directly at the interface between
two protomers (arrow). One of the N-terminal domains that line
the upper surface of the filament is circled. (b) The filament
formed in RecA crystals has a helical pitch of  83
Å and is shown with each crystallographically equivalent monomer
colored differently
(,
).
The structurally conserved ATPase
domains are in the same orientation relative to the filament
axis as in a. The crystallographically observed ADP is in
ball-and-stick form, positioned a substantial distance from the
adjacent protomer. The C-terminal domains (circled) line the
lower surface of the filament.
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