title: Binding and translocation of termination factor rho studied at the single-molecule level.
abstract: Rho termination factor is an essential hexameric helicase responsible for terminating 20-50% of all mRNA synthesis in Escherichia coli. We used single-molecule force spectroscopy to investigate Rho-RNA binding interactions at the Rho utilization site of the λtR1 terminator. Our results are consistent with Rho complexes adopting two states: one that binds 57 ± 2nt of RNA across all six of the Rho primary binding sites, and another that binds 85 ± 2nt at the six primary sites plus a single secondary site situated at the center of the hexamer. The single-molecule data serve to establish that Rho translocates 5'→3' toward RNA polymerase (RNAP) by a tethered-tracking mechanism, looping out the intervening RNA between the Rho utilization site and RNAP. These findings lead to a general model for Rho binding and translocation and establish a novel experimental approach that should facilitate additional single-molecule studies of RNA-binding proteins.
authors.affiliation: Biophysics Program, Stanford University, Stanford, CA 94305, USA.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Koslover
authors.forename: Furqan M
authors.initials: FM
authors.lastname: Fazal
authors.forename: Rachel A
authors.initials: RA
authors.lastname: Mooney
authors.forename: Robert
authors.initials: R
authors.lastname: Landick
authors.forename: Steven M
authors.initials: SM
authors.lastname: Block
mesh_terms: D001704:Biopolymers / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D021381:Protein Transport; D012234:Rho Factor / Q000378:metabolism*
chemical_list: D001704:Biopolymers; D012234:Rho Factor; D012321:DNA-Directed RNA Polymerases