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. Component of the heterotrimeric canonical replication protein A complex (RPA) (By similarity). Interacts with RPA1B, RPA2A, RPA2B and RPA2C. Belongs to the replication factor A protein 3 family.