FIG. 4.

Effects of deletions and substitutions in its repA coding sequence, and the presence of repA transcription and translation initiation signals, on the ability of the ori plasmid to be activated for replication by RepA provided in trans. Copy numbers were determined by assaying the CAT activity of E. coli strain JP3438 carrying the ori plasmids, in the absence of IPTG. The values shown are the average of at least six independent determinations. H, copy number too high to be determined accurately. Ap^R, β-lactamase gene; ▹, transcription terminator; →, RNA transcript; ––––, region deleted; RNAI.K, replacement of the sequence encoding the IncB RNAI and its target by the corresponding sequence from the IncK replicon.