Mapping of IS1 elements flanking the argF gene region on the Escherichia coli K-12 chromosome.

Two directly-repeated IS1 elements have been mapped on the Escherichia coli K-12 chromosome at positions 23.2 kb and 34.5 kb counterclockwise of the IS3 element alpha3beta3 by using F-prime plasmids (including the F lac- proAB+ plasmid F128) that carry different portions of the bacterial chromosome in the purE to proA region. Mapping was accomplished in part by construction of EcoRI, BamHI, and BglII restriction enzyme cleavage maps. Electron microscope heteroduplex and hybridization studies indicate that the chromosomal region flanked by these IS1 elements is completely homologous to the IS1-argF-IS1 region (Tn2901) on the P1argF5 transducing phage (York and Stodolsky, 1981), which suggests that the argF gene region in the usual E. coli K-12 strains has a transposon-like structure.