THE CBPA CHAPERONE GENE-FUNCTION COMPENSATES FOR DNAJ IN LAMBDA-PLASMID REPLICATION DURING AMINO-ACID STARVATION OF ESCHERICHIA-COLI

We found previously that lambda plasmid DNA replication in amino acid- starved Escherichia coli relA mutants (i.e., during the relaxed respon se), which is carried out by the inherited replication complex, is dep endent on functions of DnaK and GrpE molecular chaperones but proceeds in a dnaJ mutant at a nonpermissive temperature, Here we demonstrate that this replication is inhibited when functions of both dnaJ and cbp A are impaired, In complete media, the growth of the lambda pi A66 pha ge (capable of replicating in E. coil dnaJ, dnaK, and grpE missense mu tants at 30 degrees C), as well as efficiency of transformation by the lambda pi A66 plasmid, is significantly decreased in a dnaJ259 cbpA:: kan double mutant, These results strengthen the proposal of other auth ors (C. Ueguchi, M. Kakeda, H. Yamada, and T. Mizuno, Proc. Natl. Acad . Sci. USA 91:1054-1058, 1994; C. Ueguchi, T. Shiozama, M. Kakeda, H. Yamada, and T. Mizuno, J. Bacteriol, 177:3894-3896, 1995; and T. Yamas hino, M. Kakeda, C. Ueguchi, and T. Mizuno, Mel. Microbiol, 13:475-483 , 1994) that the cbpA gene product is a functional analog of the DnaJ chaperone in E. coli.