As part of the replication protein A (RPA/RP-A), a single-stranded DNA-binding heterotrimeric complex, may play an essential role in DNA replication, recombination and repair. Binds and stabilizes single-stranded DNA intermediates, preventing complementary DNA reannealing and recruiting different proteins involved in DNA metabolism (By similarity). Component of the heterotrimeric canonical replication protein A complex (RPA). Belongs to the replication factor A protein 3 family.