Eukaryal DMC1 proteins play a central role in homologous recombination in
meiosis by assembling at the sites of programmed DNA double-strand breaks and
carrying out a search for allelic DNA sequences located on homologous
chromatids. They are close homologs of eukaryal Rad51 and archaeal RadA proteins
and are remote homologs of bacterial RecA proteins. These recombinases (also
called DNA strand-exchange proteins) promote a pivotal strand-exchange reaction
between homologous single-stranded and double-stranded DNA substrates. An
octameric form of a truncated human DMC1 devoid of its small N-terminal domain
(residues 1-83) has been crystallized. The structure of the truncated DMC1
octamer is similar to that of the previously reported full-length DMC1 octamer,
which has disordered N-terminal domains. In each protomer, only the ATP cap
regions (Asp317-Glu323) show a noticeable conformational difference. The
truncated DMC1 octamers further stack with alternate polarity into a filament.
Similar filamentous assemblies of DMC1 have been observed to form on DNA by
electron microscopy.
