RECR IS A ZINC METALLOPROTEIN FROM BACILLUS-SUBTILIS-168

The Bacillus subtilis RecR protein is required for DNA repair and reco mbination in vivo. In its N-terminal portion, RecR possesses potential zinc-ligand structures associated with the multicysteine (C-4) superf amily. The number and arrangement of the cysteine residues is suggesti ve of RecR being a-zinc-finger protein. One of the four cysteines (Cys -60) has been replaced by a Ser (C60S) or an Ala (C60A) residue to gen erate the recR60 and recRG01 genes, respectively. B. subtilis recR60, recRG01 or Delta recR1 (a null-mutant allele) cells are 10-, 134- and 144-fold more sensitive to 10 mM methanesulphonate and 95-, 900- and 1 100-fold more sensitive to the lethal effect of 100 mu M 4-nitroquinol ine-1-oxide (4NQO) than the wild-type strain, respectively. The RecR z inc-ligand C-4 motif does not seem to be accessible, because the prote in is highly resistant to oxidation and moderately resistant to reduct ion. We have determined by different biochemical methods that RecR is a zinc metalloprotein whose cysteine residues have a structural and/or functional role.