EGTA induces the synthesis in Escherichia coli of three proteins that cross-react with calmodulin antibodies

Escherichia coli mutants, (verA, dilA) specifically resistant to the Ca²⁺ channel inhibitors verapamil and diltiazem, respectively, are hypersensitive to EGTA and BAPTA. We have shown, using 1-D and 2-D gel electrophoresis, that the synthesis of at least 25 polypeptides in the mutants was enhanced by treatment with Ca²⁺ chelators and the synthesis of at least 11 polypeptides was repressed. This pattern of induction was not observed in heat- or SDS-treated cells and therefore does not appear to be a general stress response. The majority of the induced proteins are low molecular weight, extremely heat stable and acidic, characteristic properties of calmodulin. Moreover, of the major induced species, three with apparent molecular masses of 12, 18, and 34kDa all cross-reacted with polyclonal and monoclonal antibodies to eukaryote calmodulins or calerythrin, a heat-resistant Ca²⁺-binding protein from Saccharo-polyspora erythraea. The verA, dilA mutants. In being hypersensitive to EGTA and to the Ca²⁺ ionophore A23187 + Ca²⁺, may be defective in the regulation of the level of free intracellular Ca²⁺.