Identification of the E. coli dnaJ gene product

SummaryWe have previously shown that a mutation (groPC259) in the E. coli dnaJ gene renders the cell inviable at high temperatures and arrests bacteriophage λ DNA replication at all temperatures (Sunshine et al., 1977). We have isolated λdnaJ++ transducing phages both by in vitro cloning and by abnormal excision of a λdnaK transducing phage integrated near the dnaJ locus. The dnaJ gene product has been identified on SDS polacrylamide gels after infection of UV-irradiated E. coli cells by λdnaJ++ derivative phages. It is a polypeptide chain with an apparent molecular weight of 37,000-daltons. This has been verified by the fact that a transducing phage carrying an amber mutation in the dnaJ gene fails to induce the synthesis of the 37,000-dalton polypeptide chain upon infection of sup++ bacteria, but does so upon infection of supF or supD bacteria.