Abstract

When the cells of Escherichia coli mutant in heat-shock regulator protein sigma-32 were transformed with plasmid pUC19 DNA, the transformation efficiency (TR_E) of the mutant strain was about 10% of the wild type (wt) strain, indicating the role of heat-shock protein(s) in the transformation process. In order to search for the protein(s), when three different E. coli mutants in three important heat-shock proteins (DnaK, DnaJ and GroEL) were studied, TR_E of dnaK and dnaJ mutants was similar to that of their wt strain; but TR_E of groEL mutant was drastically less, that is, it is almost 10% of the TRE of its wt counterpart. On transformation of the groEL mutant with a groEL-bearing plasmid, the transformed cells elicited higher TR_E like wt cells. Over-expression of GroEL by the brief heat-shock step of the transformation procedure was also evident from immuno-precipitation, as well as western blot studies. All these results suggested that GroEL had a positive role in the transformation phenomenon.

Key words: Escherichia coli, transformation, pUC19 DNA, sigma-32, GroEL