pUB2380: characterization of a ColD-like resistance plasmid

A detailed analysis of the mobilizable, ColE1-like resistance plasmid, pUB2380, is reported. The 8.5-kb genome encodes six (possibly seven) major functions: (1) a ColD-like origin of replication, oriV, with associated replication functions, RNAI and RNAII; (2) a set of active mobilization functions highly homologous to that of ColE1, including the origin of transfer, oriT; (3) a ColE1-like multimer resolution site (cer); (4) a kanamycin-resistance determinant, aph, encoding an aminoglycoside-3'-phosphotransferase type 1; (5) an insertion sequence, IS1294; and (6) two genes, probably cotranscribed, of unknown function(s). The GC content of the various parts of the genome indicates that the plasmid is a hybrid structure assembled from DNA from at least three different sources, of which the replication region, the mobilization functions, and the resistance gene are likely to have originated in the enterobacteriaceae.