Inhibition of chaperone-dependent bacterial ribosome biogenesis.

In Escherichia coli, the molecular chaperone HSP70 (DnaK) is necessary for 30S and 50S ribosomal subunit assembly at temperatures above 37 degrees C. Inhibitors of DnaK should therefore hinder ribosome biogenesis, in addition to all of the other DnaK-dependent cellular functions. An easily testable phenotype of DnaK is described here based on alpha-complementation of beta-galactosidase. This protein fragment complementation requires a functional DnaK in vivo, offering a suitable method for screening for DnaK inhibitors. Subsequently, it will be of great importance to check whether inhibitors of bacterial DnaK selected in this way have an effect (inhibitory or stimulatory) on the activities of eukaryotic HSP70 and HSC70 chaperones, because of the universal conservation in all biota of these chaperones in both their structural and functional properties. This question is important due to their implication in many pathways in immunology, cancer biology, and neurodegenerative disorders.