Figure 4.

Regulation of the isc transcription by IscR. (A) Scheme of the 5′ limits of the isc regulatory region used to generate fragments A, B, and C cloned in front of the lacZ gene in vector pRKlacZ290. Numbers indicate the positions relative to the transcriptional start site (+1). Created in BioRender. Santos, N. (2024) BioRender.com/n65i911. (B) Cultures of NA1000 and the ΔiscR strains containing the plasmid with each distinct fusion of the isc promoter to the lacZ gene were grown in PYE medium up to midlog phase. The cultures were divided in two tubes, containing (Fe−) or not (Fe+) 100 μM 2′-2 dipyridyl and further incubated for 2 h (n = 6). (C) Cultures of NA1000 and Δfur strains containing the three transcriptional fusions were grown in PYE medium up to midlog phase. The cultures were divided in two tubes, containing PYE with no addition (Fe+), or added of 100 μM 2′-2 dipyridyl (Fe−) and further incubated for 2 h (n = 4). Promoter activity was determined by beta-galactosidase activity assays and expression is shown in Miller units (36). Statistical analysis of significance was calculated using Student’s t-test (p-values are shown above each bar).