Fig. 2: EcmrR interacts with σ⁷⁰ NCR in EcmrR-RNAP-promoter complex.

a Structure of EcmrR-promoter spacer subcomplex from EcmrR-RP_o. The unpaired adenosine and thymidine at the center of the spacer are labeled and shown as sticks. b Detailed interactions between EcmrR NTD and σ⁷⁰ NCR. The contacting residues at the EcmrR NTD and σ⁷⁰ NCR interface are superimposed with the cryo-EM densities (blue surfaces) contoured at 6σ. Hydrogen bonds and salt bridges are shown as gray dotted lines. c In vitro transcription from an EcmrR-dependent promoter using E.coli RNAP assembled with wild-type σ⁷⁰ (σ⁷⁰ WT) or σ⁷⁰ bearing mutations in the EcmrR NTD-interacting interface (R157A/D160A/K264A, designated σ⁷⁰ M1). The concentrations (in nM) of EcmrR are indicated. The experiment was repeated three times and similar results were obtained. RNA products were quantified from these three independent experiments and are shown as mean ± SD. Both of the two distinct RNA bands were quantified, and their signals are combined for plotting. d Activation of in vivo transcription from an EcmrR-dependent promoter by EcmrR WT and EcmrR bearing mutations in the σ⁷⁰ NCR-interacting interface (Y31A, N33A, D35A, F40A, or the combination of all four mutations, designated EcmrR M2). The promoter is fused to a β-galactosidase reporter gene (lacZ). Promoter activity was measured by β-galactosidase activity in miller units (MU). Expression levels of EcmrR and the loading control RpoA are shown. Data were obtained from three colonies performed in duplicate and are shown as mean ± SEM. Statistical analyses were performed using the unpaired Student’s t-test (two-tailed). **P < 0.01. Source data are provided as a Source Data file.