The overproduction of Synechocystis sp PCC 6803 heat-shock protein (Sll0170) protects Escherichia coli against high-temperature stress

摘要

The most important role of molecular chaperones, especially under extreme temperature, is in handling with the impact of such stress on proteins and avoiding loss of their native conformation. Molecular chaperones play roles in the folding, transport, synthesis and quality control of other proteins under extreme temperature. The genome of the cyanobacterium Synechocystis PCC 6803 includes three dnaK genes (encoding heat-shock protein 70, Hsp70). The role of the second Hsp70 protein (Sll0170; DnaK2) in the acquisition of thermotolerance in Escherichia coli cells was investigated. Escherichiacoli strain BL21 (DE3) was transformed with an expression vector (pTYB21) carrying the coding sequence of the Sll0170 gene under the control of the lac promoter. The recombinant cells which showed inducible expression of DnaK2 were observed to have improved viability compared to the wild-type strain upon transfer from 37 degrees C to 52 degrees C for up to 2, 4 and 6 min. Moreover, the growth of the wild-type cell culture decreased to 64% of that of the recombinant cell culture, following a transient (15 min) heat shock at 45 degrees C after which the culture was subsequently transferred back to 37 degrees C. Interestingly, the recombinant E. coli cells showed significantly faster culture growth than the wild-type cells at 37 degrees C.