RctB is a highly conserved 75.3 kD protein (658 residues), which is unique to the Vibrionaceae. The first 500 amino acids of RctB are sufficient to mediate oriCII-based replication and its C-terminal 165 residues may mediate regulatory processes. RctB contains at least three DNA binding winged-helix-turn-helix motifs, and mutations within any of these severely compromise biological activity. This entry describes domain 1 located at the N-terminal region of RctB proteins. Mutational analysis show that it binds oriCII DNA, and that this function is critical for the capacity of RctB to mediate oriCII-based replication [1].

1: The replication initiator of the cholera pathogen's second chromosome shows structural similarity to plasmid initiators. Orlova N, Gerding M, Ivashkiv O, Olinares PDB, Chait BT, Waldor MK, Jeruzalmi D; Nucleic Acids Res. 2017;45:3724-3737. PMID:28031373