The djlA gene acts synergistically with dnaJ in promoting Escherichia coli growth

Abstract

The DnaK chaperone of Escherichia coli is known to interact with the J domains of DnaJ, CbpA, and DjlA. By constructing multiple mutants, we found that the djlA gene was essential for bacterial growth above 37 degrees C in the absence of dnaJ. This essentiality depended upon the J domain of DjlA but not upon the normal membrane location of DjlA.

FIG. 1

(A) Schematic representation of the E. coli DnaJ protein family. J-dom, J domain; G/F, glycine- and phenylalanine-rich region; Zn, zinc finger domain; TM, transmembrane domain. The cross-hatched boxes indicate the conserved region in DnaJ and CbpA, the light-gray box indicates a central region of unknown function, and the darker-gray ovals indicate the J domain. The numbers refer to the amino acid residues of each protein. (B) Effects of combinations of dnaJ, cbpA, and djlA mutations on E. coli growth. Representative growth on LB agar plates following overnight incubation at various temperatures is shown. + indicates the presence of the wild-type gene, and − indicates the null mutant.

FIG. 2

Complementation of the bacterial temperature-sensitive phenotype and the block of bacteriophage λ growth of the dnaJ djlA double mutant. Strain GP110 (dnaJ djlA double mutant) was transformed with the pSE380-based constructs carrying the genes indicated at the top of the figure. Fresh transformants were grown overnight at 30°C, serially diluted, and spotted on LB agar plates containing 100 μg of ampicillin per ml at the indicated temperatures. Bacteriophage λ growth was measured as described previously (7). + indicates an average plaque size and an efficiency of plating of approximately 1.0 compared to that of the wild type, and − indicates no plaque formation (<10⁻⁵).