Genetic regulation of spy gene expression in Escherichia coli in the presence of protein unfolding agent ethanol.

In a living cell, folding of proteins is assisted by molecular chaperones and other folding helpers. In Escherichia coli (E. coli), recently an ATP independent chaperon 'Spy' was discovered which is highly up-regulated in the presence of protein unfolding agents like ethanol, butanol and tannic acid. Two response regulators; BaeR and CpxR have been recognized as transcriptional regulators of spy gene. However, the mechanism of genetic regulation of spy under protein denaturants like ethanol has not been studied in detail so far. Based on a combination of genetic, molecular biology and biochemical experimental data, we propose that BaeR protein is the primary regulator of spy gene in response to ethanol stress in E. coli. In addition, we expanded the experimental spectrum and validated that regulation of spy gene in the presence of zinc and copper metal stress is primarily via BaeR and CpxR regulators respectively. We also performed in-silico analysis to identify the homologs of Spy protein and their cognate regulatory elements in bacterial species belonging to enterobacteriaceae family. Based on the unique ATP-independent chaperone nature and genetic regulation of spy we also propose its importance in biosensor development and facilitated production of properly folded recombinant proteins.