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Topic: Helicase

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	X-Ray Crystallography Reveals Helicase that Unwinds DNA
		Helicases have become a competitive field of inquiry because defects in human forms underlie several diseases, including the cancer-prone Bloom's syndrome and a disease of premature aging called Werner syndrome.
		The large helicase donut sits atop a smaller one that is the primase, another enzyme of the replication fork.
		Richardson¹s lab prepared a helicase fragment of the helicaseprimase that was amenable to X-ray crystallography.
	www.hms.harvard.edu /news/releases/1099helicase.html (1035 words)

	BioMed Central \| Full text \| DNA unwinding assay using streptavidin-bound oligonucleotides
		Therefore, determining helicase polarity is one of the characteristics determined of a newly isolated helicase.
		It is thought that in enzymes that require forked structures, at least for the hexameric DNA helicases, the role of the non-translocating strand is to ease the exclusion of one strand from the helicase.
		Utilizing the approach to determine the directionality of several DNA helicases as a proof of concept it was shown that the approach is particularly useful to determine the directionality, and detect helicase activity, of helicases for which the currently available methods are not easily employed.
	www.biomedcentral.com /1471-2199/7/43 (3179 words)

	NationMaster - Encyclopedia: DNA helicase
		Helicase subunit in DNA polymerase is a donut-shaped enzyme and is produced by the DnaB gene.
		DNA Helicase and Exonuclease Activities Are Encoded by Distinct Domains of the WRN Gene-- An N-terminal domain in WRN was recently shown to encode a DNA sequence motif that is conserved in several exonucleases (28-30).
		Glycerol gradient centrifugation of WRN DNA helicase and exonuclease.
	www.nationmaster.com /encyclopedia/DNA-helicase (309 words)

	BioVeris Corporation \| Life Sciences -- Examples of Assay Development - Helicase (Site not responding. Last check: 2007-11-06)
		Helicases are essential enzymes that unwind DNA-DNA, DNA-RNA, or RNA-RNA duplexes by disruption of the hydrogen bonds that hold the strands together.
		Helicases are present in most organisms and are critical to numerous fundamental biological processes.
		Helicase IV, MW 75,000, is one of at least 8 helicases that have been identified in E. coli.
	www.bioveris.com /lifesciences/examples/helicase.htm (219 words)

	DNAB HELICASE HOME PAGE
		The function of DnaB helicase is to couple ATP hydroysis with the unwinding of duplex DNA at the replication fork.
		In the case of DnaB helicase, the ATP is hydrolyzed rather than synthesized and ssDNA replaces the role of the proton gate.
		The T7 helicase domain crystallized as a helix rather than a hexamer but there is good reason to expect that the monomer-monomer interfaces are the same in both the helix and the hexamer.
	chem-mgriep2.unl.edu /replic/Helicase.html (1236 words)

	ScienceDaily: X-Ray Crystallography Gives Scientists New Understanding Of Molecular Motor
		Helicases have become a competitive field of inquiry because defects in human forms underlie several diseases, including the cancer-prone Bloom's syndrome and a disease of premature aging called Werner syndrome.
		The large helicase donut sits atop a smaller one that is the primase, another enzyme of the replication fork.
		Richardson's lab prepared a helicase fragment of the helicase primase that was amenable to X-ray crystallography.
	www.sciencedaily.com /releases/1999/10/991019075233.htm (1143 words)

	Strategies for helicase recruitment and loading in bacteria
		However, the helicase complex fails to unwind the template unless the plasmid initiation protein TrfA is also present (Konieczny and Helinski, 1997).
		It is evident that the structure of the origin and the properties of the replication initiation protein contribute to the mechanism of helicase recruitment.
		LeBowitz, J.H. and McMacken, R. (1986) The Escherichia coli dnaB replication protein is a DNA helicase.
	www.nature.com /embor/journal/v4/n1/full/embor703.html (4013 words)

	RNA Helicase
		We have been studying the mechanism of RNA unwinding by a class of helicases that are involved in all aspects of RNA metabolism and in viral replication (the DExH/D subgroup of helicase superfamily 2) (27,28).
		These helicases serve as model systems for defining the behavior of DExH/D proteins in general, and more specifically, they are important drug targets in the effort to develop antiviral therapeutics.
		To deduce the molecular mechanisms of NS3 helicase activity, its role in complex contexts, and its various polymer specificities, the conventional methodologies for deconvoluting helicase mechanism are found to be inapplicable.
	www.pylelab.org /research/RNAprotein/helicases/index2.html (824 words)

	T7 Helicase
		The basic activity of a helicase is the separation of nucleic acid duplexes into their component strands, a process which is coupled to the hydrolysis of NTP's.
		There are at least 12 helicases in Escherichia coli hich perform a variety of tasks in nucleic cid metabolism, ranging from simple strand separation at the replication fork to more sophisticated processes in DNA repair and recombination.
		Helicases can be divided into two classes on the basis of mechanism, those that ranslocate in a 5'-3' direction along single-stranded DNA and those that operate with the opposite polarity.
	www.icnet.uk /labs/wigley/projects/t7helicase/t7helicase.html (439 words)

	Helicase
		The helicases are the class of enzymes responsible for the dissociation of duplex DNA into DNA single strands.
		It is noteworthy that the rates of unwinding and estimates of activities for the three helicases suggest different kinetic characteristics for these enzymes as well as different sensitivities to intercalating drugs.
		Blockade of helicase activity could result from any of these effects or a combination of them.
	www.jonathanpmiller.com /intercalation/helicase.htm (297 words)

	[No title]
		Members of this family are helicases that catalyse ATP dependent unwinding of double stranded DNA to single stranded DNA.
		The Rep family helicases are composed of four structural domains [1].
		IPR014016 Helicase superfamily 1, UvrD-related 10 - 289
	www.ebi.ac.uk /interpro/IEntry?ac=IPR000212 (236 words)

	DNA Helicase WRN
		Along with the helicase-C (carboxy-terminal helicase) domain, this region of the protein is thought to be the essential to the helicase activity of the protein (Sanger Institute- Ensembl Protein Report, 2003).
		The conserved helicase domain in the protein is shown shaded in fl, and the degree of relatedness between the proteins is shown on the right.
		Bloom Syndrome is caused by mutations of the WRN homolog BLM.
	www.bio.davidson.edu /Courses/Molbio/MolStudents/spring2003/McCord/wrn.htm (1946 words)

	A prototype molecular motor stepping on ssDNA: PcrA helicase
		DNA helicases are ATP driven molecular motors involved in all aspects of DNA metabolism, including transcription, replication and recombination.
		Monomeric PcrA helicase from Bacillus stearothermophilus is one of the smallest molecular motors known to date with full atomic scale structures available.
		PcrA helicase, a molecular motor studied from the electronic to the functional level.
	www.ks.uiuc.edu /Research/helicase (1429 words)

	Functional characterization of Helicobacter pylori DnaB helicase -- Soni et al. 31 (23): 6828 -- Nucleic Acids Research
		Helicase activity was measured in the presence of 0.9 pmol of HpDnaB and increasing amounts of 36mer oligonucleotides.
		Helicase assays were performed in the presence of various divalent cations (2 mM each) as indicated.
		Helicase reaction was carried out either using, 5'-end-labeled 18mer synthetic oligo substrate or 3'-end-labeled 18mer synthetic oligo substrate (generated by SmaI digestion of 36mer-labeled DNA annealed to M13mp19 ssDNA, M13mp19).
	nar.oxfordjournals.org /cgi/content/full/31/23/6828 (5277 words)

	Werner syndrome
		The gene for Werner disease (WRN) was mapped to chromosome 8 and cloned: by comparing its sequence to existing sequences in GenBank, it is a predicted helicase belonging to the RecQ family.
		However, it has yet to be shown to have real helicase activity (as a DNA unwinder important for DNA replication).
		The molecular role of WRN in Werner syndrome therefore remains to be proven, as does any role it might have in the aging process in general.
	www.ncbi.nlm.nih.gov /books/bv.fcgi?call=bv.View..ShowSection&rid=gnd.section.188 (238 words)

	A Chloroplast DNA Helicase II from Pea That Prefers Fork-Like Replication Structures -- Tuteja and Phan 118 (3): 1029 ...
		The direction of unwinding by helicase is defined by the strand to which the enzyme binds and moves.
		Titration of inhibition of unwinding activity of pea ctDNA helicase II by daunorubicin (A) and nogalamycin (B).
		Tuteja N, Phan T-N, Tewari KK (1996) Purification and characterization of a DNA helicase from pea chloroplast that translocates in the 3
	www.plantphysiol.org /cgi/content/full/118/3/1029 (4531 words)

	RNA helicases
		A post-doctoral researcher in our lab, Eckhard Jankowsky, discovered that NPH-II is a processive helicase that translocates along an RNA duplex in kinetic steps of approximately one half helix turn (about 6 basepairs).
		The helicase moves 3' to 5' with respect to the bottom strand of the duplex which must have a 3' single strand overhang.
		Furthermore, we try to understand which contacts the helicase makes to the RNA substrate during the unwinding reaction, which is an interesting question, since the helicase "moves" along the RNA substrate.
	cpmcnet.columbia.edu /dept/gsas/biochem/labs/pyle/research/RNAprotein/helicases/index.html (622 words)

	BioMed Central \| Full text \| The C-terminal domain of the Bloom syndrome DNA helicase is essential for genomic stability
		The helicase activity and the C-terminal domain of BLM are critical for maintaining genomic stability as measured by the sister chromatid exchange assay.
		The helicase and C-terminal mutations that fail to localize normally in the nucleolus fail to reduce the SCEs and implicate the nucleolus as a functional location for BLM during DNA replication.
		As both the helicase activity and the C-terminus of BLM are required to maintain genomic stability it is likely that the C-terminus of BLM recognizes abnormal DNA structures and the helicase activity unwinds these multi-stranded structures to engender efficient repair.
	www.biomedcentral.com /1471-2121/2/11 (6829 words)

	Helicase-dependent isothermal DNA amplification
		In living organisms, a DNA helicase is used to separate two complementary DNA strands during DNA replication (Kornberg and Baker, 1992).
		DNA helicases are found in all organisms and participate in major cellular DNA metabolisms including replication, repair and recombination (Kornberg and Baker, 1992; Caruthers and McKay, 2002).
		In a recent experiment, we were able to amplify a 2.5-kb target from a plasmid DNA by using a processive replicative helicase, T7 gene 4 protein (Y. Xu and H. Kong, unpublished data), which unwinds DNA at a rate of 300 bp/s and with high processivity (Kornberg and Baker, 1992).
	www.nature.com /cgi-taf/DynaPage.taf?file=/embor/journal/v5/n8/full/7400200.html (3846 words)

	Allosteric Effects of Nucleotide Cofactors on Escherichia coli Rep Helicase&DNA Binding -- Wong and Lohman 256 (5055): ...
		Helicase from Hepatitis C Virus, Energetics of DNA Binding.
		Unwinding of nucleic acids by HCV NS3 helicase is sensitive to the structure of the duplex.
		Escherichia coli DNA Helicase II Is Active as a Monomer.
	www.sciencemag.org /cgi/content/abstract/256/5055/350 (869 words)

	RecQ helicase, in concert with RecA and SSB proteins, initiates and disrupts DNA recombination -- Harmon and ... (Site not responding. Last check: 2007-11-06)
		that RecQ helicase binds to, and is sequestered by, scDNA (F.G. Harmon and S.C. Kowalczykowski, in prep.).
		The helicase assays were performed over a range of RecQ helicase concentrations, and the results are shown in Table 1.
		RecQ DNA helicase is a suppressor of illegitimate recombination in Escherichia coli.
	www.genesdev.org /cgi/content/full/12/8/1134 (6279 words)

	Isolation of specific and high-affinity RNA aptamers against NS3 helicase domain of hepatitis C virus -- HWANG et al. ...
		to the unwinding of RNA duplexes mediated by the HCV helicase
		Helicase reactions were performed as described above with the serially diluted substrate RNAs along with tRNA or SE RNA.
		in the fixation of the helicase conformation in an inactive
	www.rnajournal.org /cgi/content/full/10/8/1277 (8172 words)

	SciAna FilmWorks - SAFW
		The helicase domain unwinds DNA by shuttling the 3'-end of the duplex DNA away from the molecule by pulling the 5'-strand through the enzyme.
		The mechanism of unwinding is facilitated by DNA binding loops present in the helicase domain.
		This movie is based on the X-ray crystal structure of the primase and helicase domains.
	www.scianafilms.com /html/animation/features/t7/index.htm (203 words)

	[No title]
		The domain, which defines this group of proteins is found in a wide variety of helicases and helicase related proteins.
		It may be that this is not an autonomously folding unit, but an integral part of the helicase.
		The eukaryotic translation initiation factor 4A (eIF4A) is a member of the DEA(D/H)-box RNA helicase family This is a diverse group of proteins that couples an ATPase activity to RNA binding and unwinding.
	www.ebi.ac.uk /interpro/IEntry?ac=IPR001650 (557 words)

	Isolation of the Cdc45/Mcm2-7/GINS (CMG) complex, a candidate for the eukaryotic DNA replication fork helicase -- Moyer ...
		Isolation of the Cdc45/Mcm2-7/GINS (CMG) complex, a candidate for the eukaryotic DNA replication fork helicase -- Moyer et al.
		The duplex region was digested with SmaI, creating a linear plasmid with ssDNA in the middle and duplex DNA at both ends (the 5' labeled primer is 20 bases, and the 3' labeled primer is 28 bases).
		A PhosphorImager picture of DNA substrates after incubation in helicase assays with increasing amounts of CMG or Mcm4,6,7 complexes is shown.
	www.pnas.org /cgi/content/figsonly/103/27/10236 (801 words)

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