This is a family of bacterial plasmid DNA replication initiator proteins. Pfam: PF01051 is a similar family. These RepA proteins exist as monomers and dimers in equilibrium: monomers bind directly to repeated DNA sequences and thus activate replication; dimers repress repA transcription by binding an inversely repeated DNA operator. Dimer dissociation can occur spontaneously or be mediated by Hsp70 chaperones.

1: Similarities between the DNA replication initiators of Gram-negative bacteria plasmids (RepA) and eukaryotes (Orc4p)/archaea (Cdc6p). Giraldo R, Diaz-Orejas R; Proc Natl Acad Sci U S A 2001;98:4938-4943. PMID:11296251