SSB functions as a sliding platform that migrates on DNA via reptation

Ruobo Zhou, Alexander G. Kozlov, Rahul Roy, Jichuan Zhang, Sergey Korolev, Timothy M. Lohman, Taekjip Ha

Research output: Contribution to journalArticlepeer-review

121 Scopus citations


SSB proteins bind to and control the accessibility of single-stranded DNA (ssDNA), likely facilitated by their ability to diffuse on ssDNA. Using a hybrid single-molecule method combining fluorescence and force, we probed how proteins with large binding site sizes can migrate rapidly on DNA and how protein-protein interactions and tension may modulate the motion. We observed force-induced progressive unraveling of ssDNA from the SSB surface between 1 and 6 pN, followed by SSB dissociation at ∼10 pN, and obtained experimental evidence of a reptation mechanism for protein movement along DNA wherein a protein slides via DNA bulge formation and propagation. SSB diffusion persists even when bound with RecO and at forces under which the fully wrapped state is perturbed, suggesting that even in crowded cellular conditions SSB can act as a sliding platform to recruit and carry its interacting proteins for use in DNA replication, recombination and repair.

Original languageEnglish (US)
Pages (from-to)222-232
Number of pages11
Issue number2
StatePublished - Jul 22 2011
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)


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