Members of a superfamily of RecA-like recombinases facilitate a central strand
exchange reaction in the DNA repair process. Archaeal RadA and Rad51 and
eukaryal Rad51 and meiosis-specific DMC1 form a closely related group of
recombinases distinct from bacterial RecA. Nevertheless, all such recombinases
share a conserved core domain which carries the ATPase site and putative
DNA-binding sites. Here we present the crystal structure of an archaeal RadA
from Methanococcus voltae (MvRadA) in complex with ADP and Mg2+ at 2.1 A
resolution. The crystallized RadA-ADP filament has an extended helical pitch
similar to those of previously determined structures in the presence of
nonhydrolyzable ATP analogue AMP-PNP. Structural comparison reveals two
recurrent conformations with an extensive allosteric effect spanning the ATPase
site and the putative DNA-binding L2 region. Varied conformations of the L2
region also imply a dynamic nature of recombinase-bound DNA.
