The DnaK Chaperone Is Necessary for α-Complementation of β-Galactosidase in Escherichia coli

Abstract

ABSTRACT We show here the involvement of the molecular chaperone DnaK from Escherichia coli in the in vivo α-complementation of the β-galactosidase. In the dnaK756 (Ts) mutant, α-complementation occurs when the organisms are grown at 30°C but not at 37 or 40°C, although these temperatures are permissive for bacterial growth. Plasmid-driven expression of wild-type dnaK restores the α-complementation in the mutant but also stimulates it in a dnaK + strain. In a mutant which contains a disrupted dnaK gene ( ΔdnaK52 ::Cm r ), α-complementation is also impaired, even at 30°C. This observation provides an easy and original phenotype to detect subtle functional changes in a protein such as the DnaK756 chaperone, within the physiologically relevant temperature.