H. Kurumizaka et al., A CHIMERIC REC-A PROTEIN THAT IMPLICATES NON-WATSON-CRICK INTERACTIONS IN HOMOLOGOUS PAIRING, Nucleic acids research, 22(16), 1994, pp. 3387-3391
The helical filament formed by RecA protein on single-stranded DNA pla
ys an important role in homologous recombination and pairs with a comp
lementary single strand or homologous duplex DNA. The RecA nucleoprote
in filament also recognizes an identical single strand. The chimeric p
rotein, RecAc38, forms a nucleoprotein filament that recognizes a comp
lementary strand but is defective in recognition of duplex DNA, and is
associated with phenotypic defects in repair and recombination. As de
scribed here, RecAc38 nucleoprotein filament is also defective in reco
gnition of an identical strand, either when the filament has within it
a single strand or duplex DNA. A model that postulates three DNA bind
ing sites rationalizes these observations and suggests that the third
binding site mediates non-Watson-Crick interactions that are instrumen
tal in recognition of homology in duplex DNA.