E-mail: khlee@sejong.ac.krReceived April 6, 2011, Accepted April 21, 2011Psychrophilic bacteria have acquired cold-resistance in order to protect themselves against freezingtemperatures, which would otherwise be lethal. DnaK/DnaJ/GrpE systems are molecular chaperones whichfacilitate proper folding of newly synthesized proteins. Efficient folding processes are of great importanceespecially in a cold environment, such as the Arctic. In order to understand the protection mechanisms ofpsychrophilic bacteria against cold temperatures, we have explored a genome of KOPRI22215, tentativelyidentified as Psychromonas arctica, whose genome sequence has not yet been discovered. With an aim ofsearching for a coding gene of DnaK from KOPRI22215, we have applied a series of polymerase chainreactions (PCR) with homologous primers designed from other Psychromonas species and LA PCR in vitrocloning. 1917 bp complete coding sequence of dnaK from KOPRI22215 was identified including upstreampromoter sites. Recombinant plasmids to overexpress PaDnaK along with EcDnaK (DnaK of E. coli ) were thenconstructed in pAED4 vector and the pET-based system to induce PaDnaK expression by IPTG.Characterization assays of expressed PaDnaK were carried out by measuring survival rates upon 4 dayincubation at 4