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Preparation of the Mgm101 Recombination Protein by MBP-based Tagging Strategy
Published on: June 25, 2013
Homology-dependent underwinding of duplex DNA in recA protein generated paranemic complexes
1Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin--Madison 53706.
Abstract:
RecA protein promoted formation of paranemic joints, in which a recA-ssDNA complex and a nicked circular dsDNA molecule are homologously aligned without net cross-strand interwinding, is accompanied by extensive underwinding of the dsDNA molecule. When the nick is sealed by DNA ligase, a highly negatively superhelical DNA molecule is formed. This underwinding has the following properties: (a) it occurs within 2 min; (b) it is completely homology dependent; (c) it does not require a homologous free DNA end. The resulting underwound DNA species is comprised of a heterogeneous population of topoisomers. The degree of unwinding exhibits a strong dependence on the fractional length of homology in the dsDNA molecule and indicates that paranemic joints can extend for at least 2900 base pairs. The rapid underwinding associated with paranemic joint formation is followed by a longer phase in which the dsDNA molecule is more extensively underwound.
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