The WalKR two-component system controls expression of <i>spdC</i>, encoding a Abi-domain membrane protein.

<p>A. Predicted membrane topology of the SpdC protein generated using the Protter prediction tool (<a href="http://wlab.ethz.ch/protter/start/" target="_blank">http://wlab.ethz.ch/protter/start/</a>). The eight predicted transmembrane segments are numbered. Amino acids forming the putative Abi domain (based on Pfam database annotation) are shaded in green. B. Relative levels of <i>walR</i> and <i>spdC</i> transcripts were measured by qRT-PCR during growth of the HG001 Pspac<i>walRKHI</i> strain (ST1017). Bacteria were grown to exponential phase in TSB with or without increasing concentrations of IPTG to induce expression from the Pspac promoter. Expression levels were normalized using 16S rRNA as an internal standard and are indicated as <i>n</i>-fold change with respect to the control condition (absence of IPTG).