Increased sensitivity of E. coli to novobiocin, EDTA and the anticalmodulin drug W7 following overproduction of DjlA requires a functional transmembrane domain

Abstract

In earlier studies we found that E. coli is sensitive to anticalmodulin drugs such as W7. Mutants that are resistant to this drug were isolated, including wseA1. In an attempt to clone the wseA gene, we isolated a clone that restored sensitivity to the drug in the mutant. We found that this clone in fact suppresses W7 resistance through expression of djlA, which encodes a novel DnaJ-like protein. It was found previously that overproduction of DjlA could induce capsule synthesis via activation of the two-component regulatory pathway RcsC/B. In addition to suppression of wseA1, djlA overexpression increases the sensitivity of cells to EDTA and novobiocin, but not to other drugs tested. Although overexpression of a form of the protein carrying a mutation in, or lacking, the J-region of DjlA also led to increased sensitivity, indicating that the chaperone activity of this protein was not strictly required. the full-length, wild-type protein had a more pronounced effect. In contrast, a point mutation which affects the function of the transmembrane domain but not the localisation or stability of DjlA abolished the effects of DjlA overproduction.