Display Settings:

Format

Send to:

Choose Destination
We are sorry, but NCBI web applications do not support your browser and may not function properly. More information
Proc Natl Acad Sci U S A. 2003 Jul 22;100(15):8654-9. Epub 2003 Jul 11.

Chirality sensing by Escherichia coli topoisomerase IV and the mechanism of type II topoisomerases.

Author information

  • 1Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA.

Abstract

Escherichia coli topoisomerase (Topo) IV is an essential type II Topo that removes DNA entanglements created during DNA replication. Topo IV relaxes (+) supercoils much faster than (-) supercoils, promoting replication while sparing the essential (-) supercoils. Here, we investigate the mechanism underlying this chiral preference. Using DNA binding assays and a single-molecule DNA braiding system, we show that Topo IV recognizes the chiral crossings imposed by the left-handed superhelix of a (+) supercoiled DNA, rather than global topology, twist deformation, or local writhe. Monte Carlo simulations of braid, supercoil, and catenane configurations demonstrate how a preference for a single-crossing geometry during strand passage can allow Topo IV to perform its physiological functions. Single-enzyme braid relaxation experiments also provide a direct measure of the processivity of the enzyme and offer insight into its mechanochemical cycle.

PMID:
12857958
[PubMed - indexed for MEDLINE]
PMCID:
PMC166367
Free PMC Article

Images from this publication.See all images (6)Free text

Fig. 1.
Fig. 3.
Fig. 2.
Fig. 4.
Fig. 5.
Fig. 6.
PubMed Commons home

PubMed Commons

0 comments
How to join PubMed Commons

    Supplemental Content

    Icon for HighWire Icon for PubMed Central Icon for FindIt@Stanford
    Loading ...
    Write to the Help Desk