Binding dynamics of a monomeric SSB protein to DNA : a single-molecule multi-process approach
Abstract
Single-stranded DNA binding proteins (SSBs) are ubiquitous across all organisms and are characterized by the presence of an OB (oligonucleotide/oligosaccharide/oligopeptide) binding motif to recognize single-stranded DNA (ssDNA). Despite their critical role in genome maintenance, our knowledge about SSB function is limited to proteins containing multiple OB-domains and little is known about single OB-folds interacting with ssDNA. Sulfolobus solfataricus SSB (SsoSSB) contains a single OB-fold and being the simplest representative of the SSB-family may serve as a model to understand fundamental aspects of SSB:DNA interactions. Here, we introduce a novel approach based on the competition between Förster resonance energy transfer (FRET), protein-induced fluorescence enhancement (PIFE) and quenching to dissect SsoSSB binding dynamics at single monomer resolution. We demonstrate that SsoSSB follows a monomer-by-monomer binding mechanism that involves a positive-cooperativity component between adjacent monomers. We found that SsoSSB dynamic behaviour is closer to that of Replication Protein A than to Escherichia coli SSB; a feature that might be inherited from the structural analogies of their DNA-binding domains. We hypothesize that SsoSSB has developed a balance between highdensity binding and a highly dynamic interaction with ssDNA to ensure efficient protection of the genome but still allow access to ssDNA during vital cellular processes.
Citation
Morten , M J , Peregrina , J R , Figueira-Gonzalez , M , Ackermann , K , Bode , B E , White , M F & Penedo , C 2015 , ' Binding dynamics of a monomeric SSB protein to DNA : a single-molecule multi-process approach ' , Nucleic Acids Research , vol. 43 , no. 22 , pp. 10907-10924 . https://doi.org/10.1093/nar/gkv1225
Publication
Nucleic Acids Research
Status
Peer reviewed
ISSN
0305-1048Type
Journal article
Description
People Programme of the European Union’s Seventh Framework Programme [REA 334496 to B.E.B.]; Leonardo da Vinci European Union Programme (to M.F.G.); Wellcome Trust [099149/Z/12/Z, 091825/Z/10/Z]. Funding for open access charge: Wellcome Trust; University of St Andrews.Collections
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