Autoinhibition of Escherichia coli Rep monomer helicase activity by its 2B subdomain

Katherine M. Brendza, Wei Cheng, Christopher J. Fischer, Maria A. Chesnik, Anita Niedziela-Majka, Timothy M. Lohman

Research output: Contribution to journalArticlepeer-review

104 Scopus citations


DNA helicases catalyze separation of double-helical DNA into its complementary single strands, a process essential for DNA replication, recombination, and repair. The Escherichia coli Rep protein, a superfamily 1 DNA helicase, functions in DNA replication restart and is required for replication of several bacteriophages. Monomers of Rep do not display helicase activity in vitro; in fact, DNA unwinding requires Rep dimerization. Here we show that removal of the 2B subdomain of Rep to form RepA2B activates monomer helicase activity, albeit with limited processivity. Although both full length Rep and RepA2B monomers can translocate with 3′ to 5′ directionality along single-stranded DNA, the 2B subdomain inhibits the helicase activity of full length Rep. This suggests an autoregulatory mechanism for Rep helicase, which may apply to other nonhexameric helicases, whereby helicase activity is regulated by the rotational conformational state of the 2B subdomain; formation of a Rep dimer may relieve autoinhibition by altering the 2B subdomain orientation.

Original languageEnglish
Pages (from-to)10076-10081
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number29
StatePublished - Jul 19 2005


  • DNA unwinding
  • Kinetics
  • Replication
  • Translocation

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