InterPro domain: IPR035926

NusB is a prokaryotic transcription factor involved in antitermination processes, during which it interacts with the boxA portion of the mRNA nut site. Previous studies have shown that NusB exhibits an all-helical fold, and that the protein from Escherichia coli forms monomers, while Mycobacterium tuberculosis NusB is a dimer. The functional significance of NusB dimerization is unknown. An N-terminal arginine-rich sequence is the probable RNA binding site, exhibiting aromatic residues as potential stacking partners for the RNA bases. The RNA binding region is hidden in the subunit interface of dimeric NusB proteins, such as NusB from M. tuberculosis, suggesting that such dimers have to undergo a considerable conformational change or dissociate for engagement with RNA. In certain organisms, dimerization may be employed to package NusB in an inactive form until recruitment into antitermination complexes [ 1 , 2 ].

1. Solution structure of the antitermination protein NusB of Escherichia coli: a novel all-helical fold for an RNA-binding protein. EMBO J. 17, 4092-100
2. Crystal structures of the antitermination factor NusB from Thermotoga maritima and implications for RNA binding. Biochem. J. 383, 419-28