Abstract
The inhibition of plasmid ColE1 replication caused by a deletion of the ColE1 plasmid replication origin has been previously reported (T. Hashimoto-Gotoh and J. Inselburg, J. Bacteriol. 139:597-619). Evidence is presented showing that restoration of the deleted nucleotide sequence in the precise relationship it normally has to the rest of the replication region is essential for restoration of ColE1 replication capability to the deletion mutant.