title: Three-dimensional reconstruction of transcription termination factor rho: orientation of the N-terminal domain and visualization of an RNA-binding site.
abstract: The Escherichia coli rho transcription termination protein is a hexameric helicase, and is believed to function by separating an RNA-DNA hybrid. Unlike hexameric DNA helicases, where a single strand of DNA passes through the central channel, it has been proposed that the RNA wraps around the outside of the ring. We have generated a three-dimensional reconstruction of rho, and localized a tRNA molecule bound to the primary RNA-binding site to the outside of the ring. An atomic structure of the N-terminal domain of rho fits into our reconstruction uniquely, with the residues involved in RNA-binding on the outside of the ring. Although rho shares a common structural core with the F1-ATPase and other hexameric helicases, there has been a divergence in function due to rho's N-terminal domain, which has no homology to other helicases.
authors.affiliation: Department of Biochemistry and Molecular Genetics, University of Virginia Health Sciences, Charlottesville, VA, 22908-0733, USA.
authors.forename: X
authors.initials: X
authors.lastname: Yu
authors.forename: T
authors.initials: T
authors.lastname: Horiguchi
authors.forename: K
authors.initials: K
authors.lastname: Shigesada
authors.forename: E H
authors.initials: EH
authors.lastname: Egelman
mesh_terms: D001665:Binding Sites; D004926:Escherichia coli / Q000737:chemistry* / Q000235:genetics; D008854:Microscopy, Electron; D008954:Models, Biological; D008958:Models, Molecular; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D006180:Proton-Translocating ATPases / Q000737:chemistry / Q000648:ultrastructure; D012329:RNA, Bacterial / Q000235:genetics / Q000378:metabolism*; D012343:RNA, Transfer / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D012234:Rho Factor / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure*; D014158:Transcription, Genetic / Q000235:genetics
chemical_list: D012329:RNA, Bacterial; D016601:RNA-Binding Proteins; D012234:Rho Factor; D012343:RNA, Transfer; D006180:Proton-Translocating ATPases