Figure 2.

Kinetic scheme of the ColE1 replication control mechanism slightly modified from the model of Brendel and Perelson (20). The parent plasmid of pSV-no., pGEM4Z, does not produce the Rom protein. The values of parameters k₁, k₋₁, and k₂ were modified to 4.2 × 10⁷ M⁻¹⋅min⁻¹, 202 min⁻¹, and 16.5 min⁻¹, respectively, to fix the copy number of pGEM4Z at 400 per cell. Other parameters are the same as described (20). Plasmid DNA occurs either free (D) or in association with RNA II transcripts (D_II^s for short transcripts or D_II^l for longer transcripts), with RNA II primer (D_p), or with bound complex (D_c* and D_c). Short-length plasmid-bound RNA II (D_II^s) forms an unstable complex with RNA I (D_c*). Replication converts primed DNA (D_p) to free DNA (D). The conversions between the different states occur at the rates indicated.