Effect of the sequence-dependent structure of the 17 bp AT spacer on the strength of consensus-likeE.colipromotersin vivo

Three E.coli promoters with the consensus sequences in the -35 and -10 regions and the 17 bp spacer made of random, heteronomous, and of both these classes of AT DNA simultaneously were constructed and cloned into plasmid pDS3. Electrophoretic gel mobilities of restriction fragments containing these promoters indicated that bending of the latter was proportional to the number of heteronomous AT DNA tracts. The strength of these promoters in vivo measured in relation to an internal transcriptional standard was shown to correlate well with gel mobilities of the respective restriction fragments and to decrease with the number of potential DNA bending sites encoded in the promoter structure.