Purification and functional analysis of the DnaK homologue from Prevotella intermedia OMZ 326

This study examined heat shock proteins (hsps) of the periodontal pathogen Prevotella intermedia and the closely related species, Prevotella nigrescens and Prevotella corporis. After heat shock at 45 degrees C for 5 min, cell-free extracts were analysed by SDS-PAGE and Western blotting with polyclonal antibodies against Escherichia coli hsps. P. intermedia, P. nigrescens and P. corporis all expressed a DnaK homologue. The P. nigrescens DnaK was of a similar molecular mass to E. coli DnaK (70 kDa), whilst those of P. intermedia and P. corporis were approximately 69 kDa. DnaJ homologues were expressed in each species; however, no homologue of GrpE was detected. P. intermedia DnaK was purified to homogeneity by ion-exchange and affinity-chromatography, and was shown to restore activity of denatured luciferase. This molecular chaperone activity was enhanced by E. coli DnaJ and GrpE which are components of the Hsp70 molecular chaperone machine.