SOMETHING UNUSUAL: RecA of Dinococcus radiodurans binds to double standed DNA first

The D. radiodurans RecA protein (361 amino acids, Mr 38,013) is 57% identical (72% similar) to the E. coli RecA protein (352 amino acids, Mr 37,842). In vitro, the protein promotes all of the key recombino genic activities of RecA-class recombinases. It forms filaments on DNA, hydrolyses ATP and dATP in a DNA-dependent fashion and promotes DNA-strand exchange. However, the D. radiodurans RecA protein has one distinct function. The DNA strand-exchange reactions of the E. coli RecA protein, and all other homologues examined to date, are ordered so that the single-stranded DNA is generally bound first, before the double-stranded DNA is bound.