Ketones 2-heptanone, 2-nonanone, and 2-undecanone inhibit DnaK-dependent refolding of heat-inactivated bacterial luciferases in Escherichia coli cells lacking small chaperon IbpB.

Many bacteria, fungi, and plants produce volatile organic compounds (VOCs) emitted to the environment. Bacterial VOCs play an important role in interactions between microorganisms and in bacterial-plant interactions. Here, we show that such VOCs as ketones 2-heptanone, 2-nonanone, and 2-undecanone inhibit the DnaKJE-ClpB bichaperone dependent refolding of heat-inactivated bacterial luciferases. The inhibitory activity of ketones had highest effect in Escherichia coli ibpB::kan cells lacking small chaperone IbpB. Effect of ketones activity increased in the series: 2-pentanone, 2-undecanone, 2-heptanone, and 2-nonanone. These observations can be explained by the interaction of ketones with hydrophobic segments of heat-inactivated substrates and the competition with the chaperones IbpAB. If the small chaperone IbpB is absent in E. coli cells, the ketones block the hydrophobic segments of the polypeptides and inhibit the action of the bichaperone system. These results are consistent with the data on inhibitory effects of VOCs on survival of bacteria. It can be suggested that the inhibitory activity of the ketones indicated is associated with different ability of these substances to interact with hydrophobic segments in proteins.