Novel DNA binding domain and genetic regulation model of Bacillus subtilistransition state regulator AbrB

We have determined the high resolution NMR solution structure of the novel DNA binding domain of the Bacillus subtilis transition state regulator AbrB . Comparisons of the AbrB DNA binding domain with DNA binding proteins of k nown structure show that it is a member of a completely novel class of DNA recognition folds that employs a dimeric topology for cellular function. Th is new DNA binding conformation is referred to as the looped-hinge helix fo ld. Sequence homology investigations show that this DNA binding topology is found in other disparately related microbes. Structural analysis of the Ab rB DNA binding domain together with bioanalytical and mutagenic data of ful l length AbrB allows us to construct a general model that describes the gen etic regulation properties of AbrB.