Sequential assignments and secondary structure of the RNA‐binding transcriptional regulator NusB1

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Abstract
The NusB protein is involved in transcriptional regulation in bacteriophage λ. NusB binds to the RNA form of thenutsite and along with N, NusA, NusE and NusG, stabilizes the RNA polymerase transcription complex and allows stable, persistent antitermination. NusB contains a 10 residue Arg‐rich RNA‐binding motif (ARM) at the N‐terminus but is not sequentially homologous to any other proteins. In contrast to other known ARM‐containing proteins, NusB forms a stable structure in solution in the absence of RNA. NMR spectroscopy was used to determine that NusB contains six α‐helices: R10–Q21, I27–F34, V45–L65, Q79–S93, Y100–F114 and D118–L127. The structure of NusB makes it a member of a newly emerging class of α‐helical RNA‐binding proteins.