FIGURE 8.

Models for the DnaA initial complexes, including DiaA or DnaB. A, model for the basic mechanisms involved in the initiation of DNA replication. A DnaA multimer (DnaA multi) complexed with DiaA (D) is formed on oriC, followed by the timely release of DiaA and the loading of complexes of DnaB (B) and DnaC (C) (see text for details). The protein factors are depicted in different colors. IC, initiation complex; OC, open complex; ABC-IC, initiation complex including DnaABC; ABC-OC, open complex including DnaABC. The black arrows indicate formation of an open complex. B, model for the higher order structures of the initial complexes, including DiaA or DnaB. DiaA stimulates DnaA assembly on oriC, resulting in a spiral of DnaA multimers and the interaction of DiaA with specific DnaA subgroups (top). The identical DnaA subgroups are used also by the DnaB hexamer helicase following dissociation of DiaA (bottom) (see text for details). DnaA domains I–IV, DnaA Phe-46, DiaA tetramer, DnaA binding patch of DiaA, integration host factor (IHF), and DnaB hexamer are indicated in different colors. DUE (blue), DnaA boxes (R1 and R4 sites) (aqua), and ADLAS (DnaA boxes R2/R3/M, τ and I sites) (red) within oriC are also indicated.