Single-molecule measurements of the opening and closing of the DNA gate by eukaryotic topoisomerase II.

Single-molecule measurements of the opening and closing of the DNA gate by eukaryotic topoisomerase II. Research Abstract Details 

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Single-molecule measurements of the opening and closing of the DNA gate by eukaryotic topoisomerase II. Abstract Text:

Type II DNA topoisomerases are essential and ubiquitous enzymes that perform important functions in chromosome condensation and segregation and in regulating intracellular DNA supercoiling. Topoisomerases carry out these DNA transactions by passing one segment of DNA through the other by using a reversible, enzyme-bridged double strand break. The transient enzyme/DNA adduct is mediated by a phosphodiester bond between the active-site tyrosine and a backbone phosphate of DNA. The opening and closing of the DNA gate, a critical step for strand passage during the catalytic cycle, is coupled to this cleavage/religation. We designed a unique oligonucleotide substrate with a pair of fluorophores straddling the topoisomerase II cleavage site, allowing the use of FRET to monitor the opening of the DNA gate. The DNA substrate undergoes an enzyme-mediated transition between a closed and open state in the presence of ATP, similar to the overall topoisomerase II catalyzed reaction. Single-molecule fluorescence microscopy measurements demonstrate that the transition has comparable rate constants for both the opening and closing reaction during steady-state ATP hydrolysis, with an apparent equilibrium constant near unity. In the presence of AMPPNP, a reduction in FRET occurs, suggesting an opening or partial opening of the DNA gate. However, the single-molecule experiments indicate that the open and closed states do not interconvert at a measurable rate.

Single-molecule measurements of the opening and closing of the DNA gate by eukaryotic topoisomerase II. Publishing Authors By Initials

For similar biochemical phenomena, metabolism, and nutrition: biochemical phenomena: substrate specificity research abstracts see: biochemical phenomena, metabolism, and nutrition: biochemical phenomena: substrate specificity research

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Single-molecule measurements of the opening and closing of the DNA gate by eukaryotic topoisomerase II. Journal Published:

PUBLICATION TYPE: Research Support, U.S. Gov't,

Journal: Proceedings of the National Academy of Sciences of

VOLUME: 104

Page Numbers: 4840-5

Journal Abbreviation: Proc. Natl. Acad. Sci. U.S.A.

ISSN: 0027-8424

DAY: 14

MONTH: 03

YEAR: 2007

Single-molecule measurements of the opening and closing of the DNA gate by eukaryotic topoisomerase II. Information

Number of References:

LANGUAGE: eng

NlmUniqueID: 7505876

Single-molecule measurements of the opening and closing of the DNA gate by eukaryotic topoisomerase II. Keywords Mesh Terms:

KEYWORDS: Substrate Specificity

MESH TERMS: enzymology

Chemical & Substance for Abstract: Single-molecule measurements of the opening and closing of the DNA gate by eukaryotic topoisomerase II. Information

Substance Name: DNA Topoisomerases, Type II

Registry Number: EC 5.99.1.3

Grant and Affiliation Information for Single-molecule measurements of the opening and closing of the DNA gate by eukaryotic topoisomerase II.

AFFILIATION: Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA.

Country: United States

AGENCY: United States NIGMS

GRANT: GM65128

ACRONYM: GM

MEDLINETA: Proc Natl Acad Sci U S A

REFSOURCE: Proc Natl Acad Sci U S A. 2007 Mar 20;10

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