THE DNAKJ OPERON OF AGROBACTERIUM-TUMEFACIENS - TRANSCRIPTIONAL ANALYSIS AND EVIDENCE FOR A NEW HEAT-SHOCK PROMOTER

The dnaKJ operon of Agrobacterium tumefaciens was cloned and sequenced and was found to be highly homologous to previously analyzed dnaKJ op erons. Transcription of this operon in A. tumefaciens was stimulated b y heat shock as well as by exposure to ethanol and hydrogen peroxide. There were two transcripts representing the dnaKJ operon: one containi ng the dnaK and dnaJ genes and the second containing only the dnaK gen e. Primer extension analysis indicated that transcription started from the same site in heat-shocked cells and in untreated cells. The upstr eam regulatory region of the dnaKJ operon of A. tumefaciens does not c ontain the highly conserved inverted repeat sequence previously found in the groESL operon of this bacterium, as well as in many other groE and dnaK operons. Sequence analysis of the promoter region of several groESL and dnaK operons from alpha-purple proteobacteria indicates the existence of a putative promoter sequence different from the known co nsensus promoter sequences recognized by the Escherichia coli vegetati ve or heat shock sigma factor. This promoter may constitute the heat s hock promoter of these alpha-purple proteobacteria.