Effects of the uncI gene on expression of uncB, the gene coding for the a subunit of the F₁F₀ ATPase of Escherichia coli

The eight genes coding for the subunits of the E. coli F1F0 ATPase are preceded by a gene, designated uncI. A homologous gene, or a gene coding for an analagous protein, is found preceding the ATPase genes of several microorganisms. No function for the 1 gene has been described. Using lac fusions to measure gene expression in vivo, we tested the effects of deleting uncI on the expression of the adjacent gene uncB, which codes for the a subunit of the F0 sector of the ATPase. Deleting uncI reduced the expression of three uncB'-'lacZ fusion genes in vivo, but had no effect on the expression of two uncB'-'lacZ fusion genes containing a relatively smaller amount of the uncB coding region. The uncI deletion also reduced the relative synthesis of the a subunit in vitro. The I gene therefore appears to specifically affect the expression of uncB or the synthesis of the a subunit at some step after translational initiation of uncB.