PMID:23442971

Citation	Yokota, H, Chujo, YA and Harada, Y (2013) Single-molecule imaging of the oligomer formation of the nonhexameric Escherichia coli UvrD helicase. Biophys. J. 104:924-33
Abstract	Superfamily I helicases are nonhexameric helicases responsible for the unwinding of nucleic acids. However, whether they unwind DNA in the form of monomers or oligomers remains a controversy. In this study, we addressed this question using direct single-molecule fluorescence visualization of Escherichia coli UvrD, a superfamily I DNA helicase. We performed a photobleaching-step analysis of dye-labeled helicases and determined that the helicase is bound to 18-basepair (bp) double-stranded DNA (dsDNA) with a 3' single-stranded DNA (ssDNA) tail (12, 20, or 40 nt) in a dimeric or trimeric form in the absence of ATP. We also discovered through simultaneous visualization of association/dissociation of the helicase with/from DNA and the DNA unwinding dynamics of the helicase in the presence of ATP that these dimeric and trimeric forms are responsible for the unwinding of DNA. We can therefore propose a new kinetic scheme for the helicase-DNA interaction in which not only a dimeric helicase but also a trimeric helicase can unwind DNA. This is, to our knowledge, the first direct single-molecule nonhexameric helicase quantification study, and it strongly supports a model in which an oligomer is the active form of the helicase, which carries important implications for the DNA unwinding mechanism of all superfamily I helicases.
Links	PubMed PMC3576528 Online version:10.1016/j.bpj.2013.01.014
Keywords	Adenosine Triphosphate/metabolism; DNA Helicases/chemistry; DNA Helicases/metabolism; DNA, Bacterial/metabolism; DNA, Single-Stranded/metabolism; Escherichia coli/enzymology; Escherichia coli Proteins/chemistry; Escherichia coli Proteins/metabolism; Kinetics; Microscopy, Fluorescence; Photobleaching; Protein Binding; Protein Multimerization; Protein Structure, Tertiary; Protein Subunits/chemistry; Protein Subunits/metabolism
edit table

Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
ECOLI:UVRD	involved_in	GO:0051260: protein homooligomerization	ECO:0000314: direct assay evidence used in manual assertion		P		Seeded From UniProt	complete

References

See Help:References for how to manage references in GONUTS.