GroEL to DnaK chaperone network behind the stability modulation of σ32 at physiological temperature in Escherichia coli

The stability of heat-shock transcription factor σ32 in Escherichia coli has long been known to be modulated only by its own transcribed chaperone DnaK. Very few reports suggest a role for another heat-shock chaperone, GroEL, for maintenance of cellular σ32 level. The present study demonstrates in vivo physical association between GroEL and σ32 in E. coli at physiological temperature. This study further reveals that neither DnaK nor GroEL singly can modulate σ32 stability in vivo; there is an ordered network between them, where GroEL acts upstream of DnaK.