Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 102, Issue 29, Pages 10076-10081Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0502886102
Keywords
DNA unwinding; kinetics; replication; translocation
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Funding
- NIGMS NIH HHS [GM56105, GM64263, GM45948, R01 GM045948, F32 GM064263] Funding Source: Medline
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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 Rep Delta 2B activates monomer helicase activity, albeit with limited processivity. Although both full length Rep and Rep Delta 2B 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.
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