Cloning and characterization of an Escherichia coli gene, pcnB, affecting plasmid copy number.

A gene, pcnB, affecting the copy number of ColE1-related plasmids has been cloned and mapped to 3.6 min on the Escherichia coli chromosome between panD and fhu. The gene encodes a previously undescribed 48 kD protein. Several independently isolated mutants exhibiting the same phenotype, reduced copy number, have been shown to be pcnB-.