DnaK expression in response to heat shock of Streptococcus mutans.

The oral pathogen, Streptococcus mutans, persistently colonizes human hosts and initiates oral disease despite extreme variations in environmental conditions. To begin to investigate the role of the stress protein, DnaK (Hsp70), in environmental stress responses by S. mutans, pulse-chase experiments were initially used to establish that a functional heat shock response existed in this organism. A C-terminal fragment of the S. mutans dnaK gene was cloned and engineered to be expressed with a histidine tag. Using the recombinant DnaK protein that had been purified by nickel affinity chromatography, an antibody specific for the S. mutans DnaK protein was generated to analyse DnaK expression under homeostatic and heat shock conditions. Western blot analysis indicated that the anti-recombinant DnaK antibody specifically recognized a protein (molecular mass approx. 68 kDa) which was induced in response to thermal stress. Elucidating the role of DnaK in responses by S. mutans to various environmental stressors will provide a better understanding of how DnaK is involved in survival of extreme environments and the contribution of the DnaK protein to the virulence of S. mutans.