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- Title
Direct observation of base-pair stepping by RNA polymerase.
- Authors
Abbondanzieri, Elio A; Greenleaf, William J; Shaevitz, Joshua W; Landick, Robert; Block, Steven M
- Abstract
During transcription, RNA polymerase (RNAP) moves processively along a DNA template, creating a complementary RNA. Here we present the development of an ultra-stable optical trapping system with ångström-level resolution, which we used to monitor transcriptional elongation by single molecules of Escherichia coli RNAP. Records showed discrete steps averaging 3.7 +/- 0.6 A, a distance equivalent to the mean rise per base found in B-DNA. By combining our results with quantitative gel analysis, we conclude that RNAP advances along DNA by a single base pair per nucleotide addition to the nascent RNA. We also determined the force-velocity relationship for transcription at both saturating and sub-saturating nucleotide concentrations; fits to these data returned a characteristic distance parameter equivalent to one base pair. Global fits were inconsistent with a model for movement incorporating a power stroke tightly coupled to pyrophosphate release, but consistent with a brownian ratchet model incorporating a secondary NTP binding site.
- Publication
Nature, 2005, Vol 438, Issue 7067, p460
- ISSN
1476-4687
- Publication type
Journal Article
- DOI
10.1038/nature04268