The structure of the transcriptional antiterminator NusB from Escherichia coli

We have determined the solution structure of NusB, a transcription antitermination protein from Escherichia coli. The structure reveals a novel, all α-helical protein fold. NusB mutations that cause a loss of function (NusB5) or alter specificity for RNA targets (NusB101) are localized to surface residues and likely affect RNA–protein or protein–protein interactions. Residues that are highly conserved among homologs stabilize the protein core. The solution structure of E. coli NusB presented here resembles that of Mycobacterium tuberculosis NusB determined by X-ray diffraction, but differs substantially from a solution structure of E. coli NusB reported earlier.