SSB protein prevents
As helicase unwinds parental duplex, exposed single strands rapidly re-anneal due to complementarity and form secondary structures like hairpins that block polymerase progression. Single-strand binding protein homotetramer binds cooperatively with very high affinity to single-stranded DNA without sequence specificity, coating it and holding in extended conformation preventing pairing. This prevents rewinding, protects from nucleases, and removes hairpin barriers. SSB also recruits other replisome proteins such as primase and Pol III via acidic C-terminus, mechanistically coupling unwinding to synthesis and stimulating activity.
Ref: Alberts et al., Molecular Biology of the Cell, 7th ed., Chapter 5: SSB prevents reannealing and organizes lagging template