Fig. S1. Schematic representation of the domain architecture and phosphotransfer signalling in the HskA hybrid sensor kinase. The input (sensing) domain and the transmitter domain that undergoes autophosphorylation at a conserved histidine residue and transfers the phosphoryl group to the receiver domain are indicated. The HskA sensor kinase presents two PAS domains in the input region, and does not include a histidine phosphotransfer module (Hpt) module. The Hpt module would be located in a still uncharacterized separate protein. HskA is presumed to phosphorylate a response regulator, which would in turn regulate transcription of target genes. The domains receiving the phosphoryl group (receiver) and generating the output response (output) in this putative response regulator are also shown. The amino acid positions corresponding to the boundaries of each domain in HskA are indicated. The putative response regulator for HskA is unknown.

Fig. S2. Reduction of oxidized ubiquinone (UQ 0) and menadione (MK 3) by DTT. A solution containing 250 μM of UQ 0 or MK 3 was incubated for 5 min in the absence or presence of 10 mM DTT (final concentration). The absorbance spectrum of each solution was analysed using an UV/visible spectrophotometer. The figure shows the absorbance profile in each case.

Table S1. Oligonucleotides used in real-time PCR assays.

Appendix S1. Experimental procedures.

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