Polar destabilization of DNA duplexes with single-stranded overhangs by the Deinococcus radiodurans SSB protein

Julie M. Eggington, Alexander G. Kozlov, Michael M. Cox, Timothy M. Lohman

Research output: Contribution to journalArticle

18 Scopus citations

Abstract

The Deinococcus radiodurans SSB protein has an occluded site size of 50 ± 2 nucleotides on ssDNA but can form a stable complex with a 26-30-nucleotide oligodeoxynucleotide using a subset of its four ssDNA binding domains. Quantitative estimates of D. radiodurans SSB protein in the D. radiodurans cell indicate approximately 2500-3000 dimers/cell, independent of the level of irradiation. At biologically relevant concentrations, when bound at single-strand-double-strand DNA junctions in vitro, D. radiodurans SSB protein has a limited capacity to displace the shorter strand of the duplex, permitting it to bind to single-strand extensions shorter than 26-30 nucleotides. The capacity to displace the shorter strand of the duplex shows a pronounced bias for extensions with a free 3′ end. The Escherichia coli SSB protein has a similar but somewhat less robust capacity to displace a DNA strand annealed adjacent to a single-strand extension. These activities are likely to be relevant to the action of bacterial SSB proteins in double-strand break repair, acting at the frayed ends created by ionizing radiation.

Original languageEnglish
Pages (from-to)14490-14502
Number of pages13
JournalBiochemistry
Volume45
Issue number48
DOIs
StatePublished - Dec 5 2006

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