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SSB_OBF: A subfamily of OB folds similar to the OB fold of ssDNA-binding protein (SSB). SSBs bind with high affinity to ssDNA. They bind to and protect ssDNA intermediates during DNA metabolic pathways. All bacterial and eukaryotic SSBs studied to date oligomerize to bring together four OB folds in their active state. The majority (e.g. Escherichia coli SSB) have a single OB fold per monomer, which oligomerize to form a homotetramer. However, Deinococcus and Thermus SSB proteins have two OB folds per monomer, which oligomerize to form a homodimer. Mycobacterium tuberculosis SSB varies in quaternary structure from E. coli SSB. It forms a dimer of dimers having a unique dimer interface, which lends the protein greater stability. Included in this group are OB folds similar to Escherichia coli PriB. E.coli PriB is homodimeric with each monomer having a single OB fold. It does not appear to form higher order oligomers. PriB is an essential protein for the replication restart at forks that have stalled at sites of DNA damage. It also plays a role in the assembly of primosome during replication initiation at the bacteriophage phiX174 origin. PriB physically interacts with SSB and binds ssDNA with high affinity.
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