Insertion of IS4 into the tnpA gene of Tn3: sequencing of the insertion site.

Plasmid pMM237 lacks the deletion-forming activity associated with its Tn3 transposase-encoding gene (mpA) [Morita et al., J. Biochem. 101 (1987) 1253-1264]. Analysis of the plasmid DNA showed that pMM237 was generated by insertion of IS4 into the tnpA gene of the original plasmid pMM234. The insertion was accompanied by a direct 12-bp duplication at the target site. The nucleotide sequence around the target site shared only some of the characteristics of previously reported IS4 target sites [Habermann et al., Mol. Gen. Genet. 175 (1979) 369-373; Klaer et al., Mol. Gen. Genet. 181 (1981) 169-175; Georgopoulos et al., Gene 20 (1982) 83-90; Mayaux et al., Gene 30 (1984) 137-146].