Direct observation of base-pair stepping by RNA polymerase

Article

关键词: OPTICAL FORCE CLAMP;    HAND-OVER-HAND;    SINGLE-MOLECULE;    TRANSCRIPTION ELONGATION;    STRUCTURAL BASIS;    MECHANISM;    DNA;    TRANSLOCATION;    BACKTRACKING;    KINETICS;   

DOI  :  10.1038/nature04268

来源: SCIE

【 摘 要 】

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 angstrom-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 angstrom, 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.

【 授权许可】

Free