Complete sequence of pIE545, the original Z-type plasmid

Conjugative plasmids in combination with translocatable elements play a key role in the spread of antibiotic resistance genes. The IncZ plasmid pIE545 is one of the group of plasmids that have been used since the 1980s to examine and compare the properties of conjugative plasmids in the I-complex and is the only member of the group for which a complete sequence was not available. pIE545 was found in a Klebsiella pneumoniae in Germany in the 1970s and is known to confer resistance to kanamycin, neomycin and sulphonamides. Here, the complete pIE545 sequence was determined and its structure examined. The plasmid is 109,697 bp, made up of an 86.7-kb backbone that includes determinants for replication, maintenance and conjugation functions, together with 23 kb of accessory regions. A 10.2-kb integrative element, IE-545, that interrupts the backbone impB gene is itself interrupted by an IS102-bounded transposon, TnaphA1-pIE545, that includes the aphA1 kanamycin/neomycin resistance gene and an ISEc52-like element. The sulphonamide resistance gene sul2 is in a fragment of GIsul2 inserted between nikB and trbC. An IS2 interrupts pilL, and a second copy of ISEc52-like is in one of the two additional alternate ends for the pilV gene found in the shufflon. The pIE545 shufflon is found in other backbones that contain a Z-type replicon but is distinct from the shufflons of I1- and I2-type plasmids. The uninterrupted version of IE-545 is found in both plasmids and chromosomes interrupting impB or umuC genes.