MutS mediates heteroduplex loop formation by a translocation mechanism.

Published

Journal Article

Interaction of Escherichia coli MutS and MutL with heteroduplex DNA has been visualized by electron microscopy. In a reaction dependent on ATP hydrolysis, complexes between a MutS dimer and a DNA heteroduplex are converted to protein-stabilized, alpha-shaped loop structures with the mismatch in most cases located within the DNA loop. Loop formation depends on ATP hydrolysis and loop size increases linearly with time at a rate of 370 base pairs/min in phosphate buffer and about 10,000 base pairs/min in the HEPES buffer used for repair assay. These observations suggest a translocation mechanism in which a MutS dimer bound to a mismatch subsequently leaves this site by ATP-dependent tracking or unidimensional movement that is in most cases bidirectional from the mispair. In view of the bidirectional capability of the methyl-directed pathway, this reaction may play a role in determination of heteroduplex orientation. The rate of MutS-mediated DNA loop growth is enhanced by MutL, and when both proteins are present, both are found at the base of alpha-loop structures, and both can remain associated with excision intermediates produced in later stages of the reaction.

Full Text

Duke Authors

Cited Authors

  • Allen, DJ; Makhov, A; Grilley, M; Taylor, J; Thresher, R; Modrich, P; Griffith, JD

Published Date

  • July 1997

Published In

Volume / Issue

  • 16 / 14

Start / End Page

  • 4467 - 4476

PubMed ID

  • 9250691

Pubmed Central ID

  • 9250691

Electronic International Standard Serial Number (EISSN)

  • 1460-2075

International Standard Serial Number (ISSN)

  • 0261-4189

Digital Object Identifier (DOI)

  • 10.1093/emboj/16.14.4467

Language

  • eng