FIGURE 1.

Schematic depiction of α-γ and mini α-γ replicons and a model of a preinitiation complex at α. A, schematic diagram showing the full α-γ sequence, the locations of the various iterons and half-iterons are shown. B, mini α-γ replicon formed by retaining 660 bp from the left end and deleting the remainder of the sequence all the way to, but not including the dnaA1 box of γ. C, model of a preinitiation complex formed at ori α, showing the 6 iterons of γ postulated to be wrapped around the monomeric π protein molecules, the single α iteron bound to a monomeric π and paired with the γ iteron (also bound to a monomeric π with the iteron pair stabilized by a dimeric π), and possibly a pair of DnaA proteins bound to the dnaA1 and dnaA2 boxes and containing a melted region.