Figure 3

Mutational analysis of the slr1738 and sll1621 promoter region transcriptionally fused to the cat reporter gene. The transcription start-sites (TSS, + 1) are represented as bent arrows pointing into the direction of the transcription of slr1738 (top DNA strand) and sll1621 (bottom DNA strand), respectively. The length of the cyanobacterial DNA segment between the TSS and the cat reporter gene is indicated as +120 (slr1738-cat fusion) and +73 (Sll1621-cat fusion). Nucleotide substitutions or deletions in the promoter sequences are written in bold upper cases or represented with triangles, respectively. The -35 and -10 promoter elements are boxed and shaded in gray, like the AT-rich Slr1738-binding region (Figure 5). The CAT activities determined in wild-type or Δslr1738 mutant are the average values calculated from at least 3 independent experimental repeats (standard deviations were less than 10% of sample averages). The present data indicate that this AT-rich Slr1738-binding region operate in the Slr1738-mediated negative regulation of the sll1621 promoter activity.