ROLE OF EUKARYOTIC-TYPE FUNCTIONAL DOMAINS FOUND IN THE PROKARYOTIC ENHANCER RECEPTOR FACTOR SIGMA-54

E. coli σ54 protein confers on promoters containing its recognition sequence the ability to be activated from distant DNA sites. Its functional domains include two leucine zipper motifs, an acidic region, and a glutamine-rich domain. Several domains were disrupted and the assembly of mutant transcription complexes was probed in vivo by footprinting. Promoter recognition was seen to depend on a C-terminal region containing a prokaryotic helix-turn-helix motif. Within the resulting stable closed complex, two leucine zipper motifs assist in positioning the σ54 polymerase near the DNA region that must be meited upon activation. Finally, DNA opening depends on the σ54 acid domain. The uncoupling of promoter recognition from DNA melting, mediated by the unusual domain structure of this prokaryotic protein, may be responsible for σ54's ability to mediate activation from distant sites. © 1990.