Molecular Basis of NusG-mediated Regulation of Rho-dependent Transcription Termination in Bacteria.
The bacterial transcription elongation factor NusG stimulates the Rho-dependent transcription termination through a direct interaction with Rho. The mechanistic basis of NusG dependence of the Rho function is not known. Here, we describe Rho* mutants I168V, R221C/A, and P235H that do not require NusG for their termination function. These Rho* mutants have acquired new properties, which otherwise would have been imparted by NusG. A detailed analyses revealed that they have more stable interactions at the secondary RNA binding sites of Rho, which reduced the lag in initiating its ATPase as well as the translocase activities. These more stable interactions arose from the significant spatial re-orientations of the P, Q, and R structural loops of the Rho central channel. We propose that NusG imparts similar conformational changes in the central channel of Rho, yielding faster isomerization of the open to the closed hexameric states of the latter during its RNA-loading step. This acceleration stabilizes the Rho-RNA interactions at many terminators having suboptimal rut sites, thus making Rho-NusG interactions so essential in vivo Finally, identification of the NusG binding sites on the Rho hexamer led us to conclude that the former exerts its effect allosterically.
From the Laboratory of Transcription, Center for DNA Fingerprinting and Diagnostics, Tuljaguda Complex, 4-1-714 Mozamjahi Road, Nampally, Hyderabad 500 001, India and.|the Gradutate Studies, Manipal University, Manipal, Karnataka 576104 India.
Vishalini
V
Valabhoju
From the Laboratory of Transcription, Center for DNA Fingerprinting and Diagnostics, Tuljaguda Complex, 4-1-714 Mozamjahi Road, Nampally, Hyderabad 500 001, India and.
Sonia
S
Agrawal
From the Laboratory of Transcription, Center for DNA Fingerprinting and Diagnostics, Tuljaguda Complex, 4-1-714 Mozamjahi Road, Nampally, Hyderabad 500 001, India and rsen@cdfd.org.in.
Ranjan
R
Sen
D000494:Allosteric Regulation / Q000502:physiology; D019943:Amino Acid Substitution; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D020125:Mutation, Missense; D009690:Nucleic Acid Conformation; D010445:Peptide Elongation Factors / Q000235:genetics / Q000378:metabolism*; D012329:RNA, Bacterial / Q000235:genetics / Q000378:metabolism*; D012234:Rho Factor / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D061806:Transcription Termination, Genetic / Q000502:physiology*
D029968:Escherichia coli Proteins; C070291:NusG protein, E coli; D010445:Peptide Elongation Factors; D012329:RNA, Bacterial; D012234:Rho Factor; D014157:Transcription Factors
NusG; RNA polymerase; Rho; allosteric regulation; bacteria; fluorescence; transcription termination