Origin of replication

Transcription factor

Biology

Gene

Operating system

Biophysics

Protein–protein interaction

Protein domain

Conserved sequence

Chemistry

Computer science

Linker

DNA replication

Single-stranded binding protein

DNA-binding protein

Cell biology

Base sequence

Plasma protein binding

SeqA protein domain

Biochemistry

Proceedings of the National Academy of Sciences

Bacterial single-stranded (ss)DNA-binding proteins (SSB) are essential for the replication and maintenance of the genome. SSBs share a conserved ssDNA-binding domain, a less conserved intrinsically disordered linker (IDL), and a highly conserved C-terminal peptide (CTP) motif that mediates a wide array of protein-protein interactions with DNA-metabolizing proteins. Here we show that the Escherichia coli SSB protein forms liquid-liquid phase-separated condensates in cellular-like conditions through multifaceted interactions involving all structural regions of the protein. SSB, ssDNA, and SSB-interacting molecules are highly concentrated within the condensates, whereas phase separation is overall regulated by the stoichiometry of SSB and ssDNA. Together with recent results on subcellular SSB localization patterns, our results point to a conserved mechanism by which bacterial cells store a pool of SSB and SSB-interacting proteins. Dynamic phase separation enables rapid mobilization of this protein pool to protect exposed ssDNA and repair genomic loci affected by DNA damage.

Phase separation by ssDNA binding protein controlled via protein−protein and protein−DNA interactions