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Isolation and visualization of active presynaptic filaments of recA protein and single-stranded DNA

Flory, J and Tsang, SS and Muniyappa, K (1984) Isolation and visualization of active presynaptic filaments of recA protein and single-stranded DNA. In: Proc Natl Acad Sci Unit States Am, 81 (22). pp. 7026-30.

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Official URL: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC392069...

Abstract

In the presence of ATP, recA protein forms a presynaptic complex with single-stranded DNA that is an obligatory intermediate in homologous pairing. Presynaptic complexes of recA protein and circular single strands that are active in forming joint molecules can be isolated by gel filtration. These isolated active complexes are nucleoprotein filaments with the following characteristics: (i) a contour length that is at least 1.5 times that of the corresponding duplex DNA molecule, (ii) an ordered structure visualized by negative staining as a striated filament with a repeat distance of 9.0 nm and a width of 9.3 nm, (iii) approximately 8 molecules of recA protein and 20 nucleotide residues per striation. The widened spacing between bases in the nucleoprotein filament means that the initial matching of complementary sequences must involve intertwining of the filament and duplex DNA, unwinding of the latter, or some combination of both to equalize the spacing between nascent base pairs. These experiments support the concept that recA protein first forms a filament with single-stranded DNA, which in turn binds to duplex DNA to mediate both homologous pairing and subsequent strand exchange.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to National Academy of Sciences.
Department/Centre: Division of Biological Sciences > Biochemistry
Date Deposited: 19 Feb 2010 08:36
Last Modified: 19 Sep 2010 05:55
URI: http://eprints.iisc.ernet.in/id/eprint/25676

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