Structural basis of HutP-mediated transcription anti-termination.
Abstract

Bacteria often use anti-terminator proteins to sense a specific metabolite signal and direct RNA polymerase 
to either terminate transcription or transcribe the downstream genes of an operon. Although many proteins that 
regulate various operons using this mechanism have been identified, insights into their activation processes before 
cognate mRNA binding have remained obscure. HutP from Bacillus subtilis regulates the hut operon by an anti-termination 
mechanism. Recently, several crystal structures of HutP [apo-HutP, HutP-L-histidine (and histidine analog), 
HutP-L-histidine-Mg(2+) and HutP-L-histidine-Mg(2+)-RNA] have been reported. These structural and functional 
studies of HutP have revealed how the protein undergoes conformational changes in response to two key components: L-histidine and Mg(2+) ions.