MutS recognizes misspaired bases and it is required to activate downstream events in the postreplicative DNA Mismatch Repair System. In a previous work, we determined that the C-terminal region of P. aeruginosa MutS is involved in the interaction with other factor necessary for the correct function of the MRS. To analyze if the C-terminal region of MutS (Cter) interacts with other protein, the DNA encoding this domain was fused in frame to the maltose binding protein (MBP) gene, and expressed in P. aeruginosa. The purified MBP-Cter protein consistently copurified with the chaperone DnaK, which was absent in MBP purified preparations. The P. aeruginosa cells expressing the fusion MBPCter acquired a phenotype similar to that previously described for dnaK mutants in other bacteria: diminished viability, cell filamentation and high temperature sensitivity. Similar phenotypes were detected by overexpressing the full length MutS protein. On the contrary, overexpression of a C-terminal deletion MutS mutant did not produce phenotypic changes compared to the wild type strain. We propose that DnaK interacts with the C-terminal region of MutS and the overexpression of the repair protein produces a complete sequestration of DnaK. We are currently analyzing the interaction MutS-DnaK in vitro and generating P. aeruginosa dnaK mutant strains to characterize its phenotype.