Single-strand binding protein

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Single-strand binding protein, also known as SSB or SSBP, binds single stranded regions of DNA to prevent premature reannealing. The strands have a natural tendency to revert to the duplex form, but SSB binds to the single strands, keeping them separate and allowing the DNA replication machinery to perform its function.

SSB proteins have been identified in organisms from viruses to humans. While many phage and viral SSBs function as monomers and eukaryotes tend to encode heterotrimeric RPA (Replication Protein A), the best characterized SSB is that from the bacteria E. coli which, like most bacterial SSBs exists as a tetramer. An active SSB is composed of four identical subunits, each with a molecular weight of 18 843 Da. Binding of single-stranded DNA to the tetramer can occur in different "modes", with SSB occupying different numbers of DNA bases depending on a number of factors, including salt concentration.

[edit] See also

• DNA-binding protein

[edit] External links

• MeSH Single-Stranded+DNA+Binding+Proteins

v • d • e DNA replication Origin of replication/Ori/Replicon - DNA clamp - Okazaki fragment - Replication fork (Lagging and leading strands) - Single-strand binding protein - Primer - Processivity - Klenow fragment Pre-replication complex: Helicase (dnaA, dnaB, T7) - Primase (dnaG) - DNA polymerase III holoenzyme (dnaQ) DNA ligase - Telomerase - Topoisomerase