title: Domain interactions of the transcription-translation coupling factor Escherichia coli NusG are intermolecular and transient.
abstract: The bacterial transcription factor NusG (N-utilization substance G) is suggested to act as a key coupling factor between transcription and translation [Burmann, Schweimer, Luo, Wahl, Stitt, Gottesman and Rösch (2010) Science 328, 501-504] and contributes to phage λ-mediated antitermination in Escherichia coli that enables read-through of early transcription termination sites. E. coli NusG consists of two structurally and functionally distinct domains that are connected through a flexible linker. The homologous Aquifex aeolicus NusG, with a secondary structure that is highly similar to E. coli NusG shows direct interaction between its N- and C-terminal domains in a domain-swapped dimer. In the present study, we performed NMR paramagnetic relaxation enhancement measurements and identified interdomain interactions that were concentration dependent and thus probably not only weak and transient, but also predominantly intermolecular. This notion of two virtually independent domains in a monomeric protein was supported by 15N-relaxation measurements. Thus we suggest that a regulatory role of NusG interdomain interactions is highly unlikely.
authors.affiliation: Lehrstuhl für Biopolymere and Research Centre for Biomacromolecules, Universität Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany.
authors.forename: Björn M
authors.initials: BM
authors.lastname: Burmann
authors.forename: Ulrich
authors.initials: U
authors.lastname: Scheckenhofer
authors.forename: Kristian
authors.initials: K
authors.lastname: Schweimer
authors.forename: Paul
authors.initials: P
authors.lastname: Rösch
mesh_terms: D003001:Cloning, Molecular; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D010445:Peptide Elongation Factors / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D013997:Time Factors; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D029968:Escherichia coli Proteins; C070291:NusG protein, E coli; D010445:Peptide Elongation Factors; D014157:Transcription Factors