Binding and Translocation of Termination Factor Rho Studied at the Single-Molecule Level

作者：Koslover Daniel J; Fazal Furqan M; Mooney Rachel A; Landick Robert; Block Steven M^*

来源：Journal of Molecular Biology, 2012, 423(5): 664-676.

DOI：10.1016/j.jmb.2012.07.027

• RNA polymerase
• transcription
• optical trap
• single-molecule biophysics
• force spectroscopy

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 lambda tR1 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 +/- 2 nt 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.

• 出版日期2012-11-9