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Structure of a Mycobacterium tuberculosis NusA–RNA complex
Author(s) -
Beuth Barbara,
Pennell Simon,
Arnvig Kristine B,
Martin Stephen R,
Taylor Ian A
Publication year - 2005
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1038/sj.emboj.7600829
Subject(s) - library science , division (mathematics) , biology , sociology , operations research , computer science , engineering , arithmetic , mathematics
NusA is a key regulator of bacterial transcriptional elongation, pausing, termination and antitermination, yet relatively little is known about the molecular basis of its activity in these fundamental processes. In Mycobacterium tuberculosis , NusA has been shown to bind with high affinity and specificity to BoxB–BoxA–BoxC antitermination sequences within the leader region of the single ribosomal RNA (rRNA) operon. We have determined high‐resolution X‐ray structures of a complex of NusA with two short oligo‐ribonucleotides derived from the BoxC stem–loop motif and have characterised the interaction of NusA with a variety of RNAs derived from the antitermination region. These structures reveal the RNA bound in an extended conformation to a large interacting surface on both KH domains. Combining structural data with observed spectral and calorimetric changes, we now show that NusA binding destabilises secondary structure within rRNA antitermination sequences and propose a model where NusA functions as a chaperone for nascently forming RNA structures.