Substitutions in the Escherichia coli RNA polymerase sigma70 factor that affect recognition of extended -10 elements at promoters.

Previous work has shown that the base sequence of the DNA segment immediately upstream of the -10 hexamer at bacterial promoters (the extended -10 element) can make a significant contribution to promoter strength. Guided by recently published structural information, we used alanine scanning and suppression mutagenesis of Region 2.4 and Region 3.0 of the Escherichia coli RNA polymerase sigma(70) subunit to identify amino acid sidechains that play a role in recognition of this element. Our study shows that changes in these regions of the sigma(70) subunit can affect the recognition of different extended -10 element sequences.