Bacillus subtilis tetA (L) gene expression: evidence for regulation by translational reinitiation

The tetA (L) gene of Bacillus subtilis encodes a transmembrane protein that can function as a Tc-metal/H⁺ antiporter, conferring low-level resistance to tetracycline. The TetA(L) coding sequence is preceded by a leader region that contains a 20-amino-acid open reading frame and an appropriately spaced ribosome binding site. Expression of the gene is induced by addition of tetracycline, which is thought to act by binding to ribosomes that translate the tetA (L) leader peptide coding sequence. Here we demonstrate that induction of tetA (L) expression includes minor transcriptional and major translational components. Deletion and point mutations of the tetA (L) leader region were constructed to probe the mechanism of translational induction. To account for the observed mutant phenotypes, we propose that tetA (L) expression is regulated by a translational reinitiation mechanism.