Region 1.1 modulates DNA binding by region 2 and 4 when sigma is unbound by the core RNA polymerase [1,2]. Region 1.1 is also involved in promoter binding [1]

1: A mutation in region 1.1 of sigma70 affects promoter DNA binding by Escherichia coli RNA polymerase holoenzyme. Bowers CW, Dombroski AJ; EMBO J 1999;18:709-716. PMID:9927430

2: Effects of amino acid substitutions at conserved and acidic residues within region 1.1 of Escherichia coli sigma(70). Bowers CW, McCracken A, Dombroski AJ; J Bacteriol 2000;182:221-224. PMID:10613885