Insertions of transposable elements in the promoter proximal region of the gene cluster for Escherichia coli H+-ATPase: 8 base pair repeat generated by insertion of IS1.

A plasmid pKY159 (Yamaguchi and Yamaguchi 1983) carrying a promoter proximal portion of the gene cluster of the proton-translocating ATPase (H+-ATPase) of Escherichia coli causes growth inhibition of wild-type cells. Insertion of a transposable element in this plasmid released this inhibitory effect. In analyzing this inhibitory effect, we determined the insertion points at the nucleotide-sequence level of transposable elements on 30 independent derivatives of pKY159 . Insertions of IS1, IS5, and gamma delta were found between the promoter and the gene for a possible component of 14,000 daltons of the H+-ATPase. Of 31 insertions, 26 were of IS1 and were located at the same site, indicating that this site is a hotspot for IS1 insertion and that IS1 insertion is much more frequent than that of IS5 or gamma delta in this region. Four different sites for IS1 insertion were found; in two of these an 8 base pair (bp) duplicate of the target sequence ( AAAAACGT and AAACGTTG ) was generated, while in the other two a 9 bp duplicate was found. In all cases in this study the nucleotide sequence of IS1 was the same as that of IS1-K. In the two cases with an 8 bp duplicate in different sites, a common 6 bp sequence ( AAACGT ) was found. These results suggested that generation of the 8 bp duplicate is related to the common sequence rather than a mutation in IS1 suggested by Iida et al. (1981) and also suggested that the essential length of the duplicate is 8 bp or less than 8 bp. A 6 bp sequence ( GTGATG ) homologous to the end portion of IS1 was found at the hotspot , but not at other sites, suggesting that this homology contributed to the high frequency of IS1 insertion.(ABSTRACT TRUNCATED AT 250 WORDS)