MUTANT RECA PROTEINS WHICH FORM HEXAMER-SIZED OLIGOMERS

We have analyzed the oligomeric properties of a number of mutant RecA proteins containing single amino acid substitutions within one region of the subunit interface. In contrast to wild-type RecA, which forms a heterogeneous population of different-sized oligomers, we find that m any of these mutant proteins exist in a more homogeneous oligomeric fo rm, which approximates to the size of a RecA hexamer. Some of these mu tants have a significant level of activity in vivo for recombinational DNA repair and thus represent the first mutant RecA proteins identifi ed which retain activity yet can exist in a discrete oligomeric state as free protein. (C) 1997 Academic Press Limited.