The Pseudomonas aeruginosa hscA gene encodes Hsc66, a DnaK homologue

Under heat-stress conditions bacteria induce, among other heat-shock protei ns, the Hsp70 molecular chaperone (DnaK), which is involved in protein stab ilization. It has been shown in Escherichia coli that an Hsp70 homologue ca lled Hsc66, which is widespread in bacteria, functions as a chaperone in vi tro. This paper reports the isolation of a Pseudomonas aeruginosa W51D muta nt (W51M22) by insertion of the mini-Tn5-Hg transposon, which was unable to grow on ethanol and other short-chain alcohols as sole source of carbon. T he transposon insertion in this mutant was shown to be located in the hscA gene encoding Hsc66. The inability of mutant W51M22 to use ethanol was comp lemented by the E. coil hscBA-fdx operon. The authors characterized the tra nscriptional arrangement of hscA, showing that it forms part of an operon w ith the upstream hscB gene, and that it is also expressed from its own prom oter. These results are compatible with the P. aeruginosa Hsc66 protein bei ng a functional molecular chaperone involved in the stabilization, in the p resence of ethanol, of some proteins required for bacterial growth on short -chain alcohols.