Physiological roles of the DnaK and GroE stress proteins: catalysts of protein folding or macromolecular sponges?

When organisms ranging from microbes to man are subjected to certain environmental stresses a characteristic 'heat shock' response is observed. In Escherichia coli this response is characterized by the induction of several proteins, three of which are the 70 kilodalton product of the dnaK gene, the 60 kilodalton product of the groEL (mopA) gene and the 15 kilodalton product of the groES (mopB) gene. In this review, utilizing enteric bacteria as model organisms, we focus on the role of these proteins within the context provided by well-established functions of other heat shock products. These facts serve as a starting point from which to speculate upon the in vivo role of these proteins during steady-state growth.