Linked Life Data

10543970

Source:http://linkedlifedata.com/resource/pubmed/id/10543970

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
4
pubmed:dateCreated
1999-12-30
pubmed:abstractText
Pre-steady-state chemical quenched-flow techniques were used to study DNA unwinding catalyzed by Escherichia coli UvrD helicase (helicase II), a member of the SF1 helicase superfamily. Single turnover experiments, with respect to unwinding of a DNA oligonucleotide, were used to examine the DNA substrate and UvrD concentration requirements for rapid DNA unwinding by pre-bound UvrD helicase. In excess UvrD at low DNA concentrations (1 nM), the bulk of the DNA is unwound rapidly by pre-bound UvrD complexes upon addition of ATP, but with time-courses that display a distinct lag phase for formation of fully unwound DNA, indicating that unwinding occurs in discrete steps, with a "step size" of four to five base-pairs as previously reported. Optimum unwinding by pre-bound UvrD-DNA complexes requires a 3' single-stranded (ss) DNA tail of 36-40 nt, whereas productive complexes do not form readily on DNA with 3'-tail lengths </=16 nt. A 5'-ssDNA tail is neither sufficient nor does it stimulate unwinding, even in the presence of a 3'-ssDNA tail. Nitrocellulose filter binding studies show that UvrD binding affinity also increases with increasing 3'-ssDNA tail length, showing apparent positive cooperativity for binding to DNA with a 40 nt 3'-ssDNA tail. Single turnover DNA unwinding experiments performed at higher DNA concentrations (50 nM) show a sigmoidal dependence of the extent of unwinding on the pre-incubated [UvrD], also indicating cooperativity. These results indicate that the form of the UvrD helicase with optimal helicase activity is oligomeric with at least two sites for binding the DNA substrate, where one site contacts regions of the 3'-ssDNA tail that are distal from the single-stranded/double-stranded DNA junction.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Nov
pubmed:issn
0022-2836
pubmed:author
pubmed:copyrightInfo
Copyright 1999 Academic Press.
pubmed:issnType
Print
pubmed:day
5
pubmed:volume
293
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
815-34
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
1999
pubmed:articleTitle
An oligomeric form of E. coli UvrD is required for optimal helicase activity.
pubmed:affiliation
Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, MO 63110, USA.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S.