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. Author manuscript; available in PMC: 2014 May 1.
Published in final edited form as: Plasmid. 2013 Mar 5;69(3):231–242. doi: 10.1016/j.plasmid.2013.02.003

Figure 1.

Figure 1

Salient features of plasmid R6K. Parental R6K has 3 replication origins, α, γ and β. Only γ ori and the pir gene product, π, (expanded view) are required for a minimal replicon. White arrowheads represent ‘TGAGnG-motif’ binding sites for π (in γ ori). π is multi-functional (see key.) Operator occupancy results in π autorepression while initiation is controlled, in part, by differential occupancy of the direct repeats adjacent to an A+T-rich region. Dimerization of π (black arrow) is largely irreversible (gray arrow), however π monomers have greater affinity for the 7 direct repeats than do dimers. Figure is not drawn to scale.