title: A bacterial transcription terminator with inefficient molecular motor action but with a robust transcription termination function.
abstract: Molecular motors such as helicases/translocases are capable of translocating along the single-stranded nucleic acids and unwinding DNA or RNA duplex substrates using the energy derived from their ATPase activity. The bacterial transcription terminator, Rho, is a hexameric helicase and releases RNA from the transcription elongation complexes by an unknown mechanism. It has been proposed, but not directly demonstrated, that kinetic energy obtained from its molecular motor action (helicase/translocase activities) is instrumental in dissociating the transcription elongation complex. Here we report a hexameric Rho analogue (Rv1297, M. tb. Rho) from Mycobacterium tuberculosis having poor RNA-dependent ATP hydrolysis and inefficient DNA-RNA unwinding activities. However, compared to Escherichia coli Rho, it exhibited very robust and earlier transcription termination from the elongation complexes of E. coli RNA polymerase. Bicyclomycin, an inhibitor of ATPase as well as RNA release activities of E. coli Rho, inhibited the ATPase activity of M. tb. Rho with comparable efficiency but was not efficient in inhibiting its transcription termination function. Unlike E. coli Rho, M. tb. Rho was capable of releasing RNA in the presence of nonhydrolyzable analogues of ATP quite efficiently. Also, this termination function most likely does not require NusG, an RNA-release facilitator, as this Rho was incapable of binding to NusG either of M. tb. (Rv0639) or E. coli. These results strongly suggest that the ATPase activity of M. tb. Rho is uncoupled from its transcription termination function and this function may not be dependent on its helicase/translocase activity.
authors.affiliation: Laboratory of Transcription Biology, Center for DNA Fingerprinting and Diagnostics, Tuljaguda Complex, 4-1-714 Mozamjahi Road, Nampally, Hyderabad-500 001, India.
authors.forename: Nisha C
authors.initials: NC
authors.lastname: Kalarickal
authors.forename: Amitabh
authors.initials: A
authors.lastname: Ranjan
authors.forename: B Sudha
authors.initials: BS
authors.lastname: Kalyani
authors.forename: Megha
authors.initials: M
authors.lastname: Wal
authors.forename: Ranjan
authors.initials: R
authors.lastname: Sen
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D004269:DNA, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D008958:Models, Molecular; D020409:Molecular Motor Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009169:Mycobacterium tuberculosis / Q000235:genetics / Q000378:metabolism*; D010445:Peptide Elongation Factors / Q000235:genetics / Q000378:metabolism; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D012329:RNA, Bacterial / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D020409:Molecular Motor Proteins; C070291:NusG protein, E coli; D010445:Peptide Elongation Factors; D012329:RNA, Bacterial; D016601:RNA-Binding Proteins; C534627:Rho protein, E coli; D014157:Transcription Factors; D000251:Adenosine Triphosphatases