The sigma subunit of Escherichia coli RNA polymerase senses promoter spacing

A. J. Dombroski, B. D. Johnson, M. Lonetto, C. A. Gross
1996 Proceedings of the National Academy of Sciences of the United States of America  
The promoters recognized by or7r, the primary sigma ofEscherichia coli, consist of two highly conserved hexamers located at -10 and -35 bp from the start point of transcription, separated by a preferred spacing of 17 bp. a, factors have two distinct DNA binding domains that recognize the two hexamer sequences. However, the component of RNA polymerase recognizing the length of the spacing between hexamers has not been determined. Using an equilibrium DNA binding competition assay, we demonstrate
more » ... that a polypeptide of cr70 carrying both DNA binding domains is very sensitive to promoter spacing, whereas a cr70 polypeptide with only one DNA binding domain is not. Furthermore, a mutant cr, selected for increasing transcription of the minimal lac promoter (18-bp spacer), has an altered response to promoter spacing in vivo and in vitro. Our data support the idea that a, makes simultaneous, productive contacts at both the -10 and the -35 regions of the promoter and discerns the spacing between these conserved regions.
doi:10.1073/pnas.93.17.8858 pmid:8799117 pmcid:PMC38558 fatcat:vx53lpigkvbgfczlkastlio5su