title: Autoinhibition of Escherichia coli Rep monomer helicase activity by its 2B subdomain.
abstract: 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 RepDelta2B activates monomer helicase activity, albeit with limited processivity. Although both full length Rep and RepDelta2B 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.
authors: Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA.
authors: Katherine M
authors: KM
authors: Brendza
authors: Wei
authors: W
authors: Cheng
authors: Christopher J
authors: CJ
authors: Fischer
authors: Marla A
authors: MA
authors: Chesnik
authors: Anita
authors: A
authors: Niedziela-Majka
authors: Timothy M
authors: TM
authors: Lohman
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D004265:DNA Helicases / Q000378:metabolism*; D004261:DNA Replication / Q000502:physiology*; D004277:DNA, Single-Stranded / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins; D008958:Models, Molecular; D017434:Protein Structure, Tertiary
chemical_list: D004277:DNA, Single-Stranded; D004791:Enzyme Inhibitors; D029968:Escherichia coli Proteins; C506744:rep protein, E coli; D000251:Adenosine Triphosphatases; D004265:DNA Helicases