The DNA-binding domain in the Bacillus subtilis transition-state regulatorAbrB employs significant motion for promiscuous DNA recognition

AbrB is a Bacillus subtilis protein responsible for regulating a diverse ar ray of unrelated genes during periods of sub-optimal growth conditions. DNA binding by AbrB is unique in that sequence recognition is specific, yet no obvious consensus sequence of bound promoter regions is apparent. The N-te rminal domain is a recently characterized representative of a novel class o f DNA-binding proteins that possess a looped hinge helix DNA-binding topolo gy. Although the structural characterization of this DNA-binding topology c ontributed to an understanding of the architectural basis for recognition o f DNA target sequences, specific mechanisms responsible for promiscuity in DNA sequence recognition still were not apparent. Analysis of N-15 backbone relaxation parameters shows that dynamic motion of regions directly linked to DNA binding show concerted motion on the microsecond-millisecond timesc ale. Furthermore, dynamic motion of the hinge region suggests that the DNA- binding region is capable of conformational orientations that allow it to a ccommodate DNA sequence variability in the cognate binding sites. (C) 2001 Academic Press.