Linked Life Data

19094994

Source:http://linkedlifedata.com/resource/pubmed/id/19094994

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
5
pubmed:dateCreated
2009-2-2
pubmed:abstractText
DNA topoisomerases control the topology of DNA (e.g., the level of supercoiling) in all cells. Type IIA topoisomerases are ATP-dependent enzymes that have been shown to simplify the topology of their DNA substrates to a level beyond that expected at equilibrium (i.e., more relaxed than the product of relaxation by ATP-independent enzymes, such as type I topoisomerases, or a lower-than-equilibrium level of catenation). The mechanism of this effect is currently unknown, although several models have been suggested. We have analyzed the DNA relaxation reactions of type II topoisomerases to further explore this phenomenon. We find that all type IIA topoisomerases tested exhibit the effect to a similar degree and that it is not dependent on the supercoil-sensing C-terminal domains of the enzymes. As recently reported, the type IIB topoisomerase, topoisomerase VI (which is only distantly related to type IIA enzymes), does not exhibit topology simplification. We find that topology simplification is not significantly dependent on circle size in the range approximately 2-9 kbp and is not altered by reducing the free energy available from ATP hydrolysis by varying the ADP:ATP ratio. A direct test of one model (DNA tracking; i.e., sliding of a protein clamp along DNA to trap supercoils) suggests that this is unlikely to be the explanation for the effect. We conclude that geometric selection of DNA segments by the enzymes is likely to be a primary source of the effect, but that it is possible that other kinetic factors contribute. We also speculate whether topology simplification might simply be an evolutionary relic, with no adaptive significance.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Feb
pubmed:issn
1089-8638
pubmed:author
pubmed:issnType
Electronic
pubmed:day
6
pubmed:volume
385
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
1397-408
pubmed:dateRevised
2010-11-18
pubmed:meshHeading
pubmed:year
2009
pubmed:articleTitle
How do type II topoisomerases use ATP hydrolysis to simplify DNA topology beyond equilibrium? Investigating the relaxation reaction of nonsupercoiling type II topoisomerases.
pubmed:affiliation
Department of Biological Chemistry, John Innes Centre, Colney, Norwich, UK.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't, Research Support, N.I.H., Extramural