title: 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 high-density 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.
authors.affiliation: Biomedical Sciences Research Complex, University of St Andrews, St Andrews, Fife KY16 9ST, UK.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Morten
authors.affiliation: Biomedical Sciences Research Complex, University of St Andrews, St Andrews, Fife KY16 9ST, UK.
authors.forename: Jose R
authors.initials: JR
authors.lastname: Peregrina
authors.affiliation: Biomedical Sciences Research Complex, University of St Andrews, St Andrews, Fife KY16 9ST, UK.
authors.forename: Maria
authors.initials: M
authors.lastname: Figueira-Gonzalez
authors.affiliation: Biomedical Sciences Research Complex, University of St Andrews, St Andrews, Fife KY16 9ST, UK EaStCHEM School of Chemistry and Centre of Magnetic Resonance, University of St Andrews, St Andrews, Fife KY16 9ST, UK.
authors.forename: Katrin
authors.initials: K
authors.lastname: Ackermann
authors.affiliation: Biomedical Sciences Research Complex, University of St Andrews, St Andrews, Fife KY16 9ST, UK EaStCHEM School of Chemistry and Centre of Magnetic Resonance, University of St Andrews, St Andrews, Fife KY16 9ST, UK.
authors.forename: Bela E
authors.initials: BE
authors.lastname: Bode
authors.affiliation: Biomedical Sciences Research Complex, University of St Andrews, St Andrews, Fife KY16 9ST, UK mf2@st-andrews.ac.uk.
authors.forename: Malcolm F
authors.initials: MF
authors.lastname: White
authors.affiliation: Biomedical Sciences Research Complex, University of St Andrews, St Andrews, Fife KY16 9ST, UK SUPA School of Physics and Astronomy, University of St Andrews, St Andrews, Fife KY16 9SS, UK jcp10@st-andrews.ac.uk.
authors.forename: J Carlos
authors.initials: JC
authors.lastname: Penedo
mesh_terms: D019843:Archaeal Proteins / Q000378:metabolism*; D004277:DNA, Single-Stranded / Q000737:chemistry / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D031541:Fluorescence Resonance Energy Transfer; D011485:Protein Binding; D048229:Sulfolobus solfataricus
chemical_list: D019843:Archaeal Proteins; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins