Suppressor mutations identified in uncharacterized TCS signaling genes.

Suppressor strains were sequenced with the Illumina MiSeq platform and compared to the annotated M. xanthus DK1622 genome [27]. (A) Genomic organization of the locus containing the RR gene mxan_4240 (nmpR) (B) and SK gene mxan_4246 (nmpU) (C). This locus also contains a gene encoding a protein with two RR receiver domains (mxan_4245, nmpT, RR-RR) and an atypical hybrid response regulator/sensor kinase (mxan_4244, nmpS, RR-SK). The results of the mutations are depicted (B and C): a missense mutation in nmpR (V87E) and premature stop codons (stop signs) or frameshifts (Δ-1) in nmpU. The location of the mutations within each protein is to scale. The positions of each domain of these proteins is also indicated by amino acid number (RR = response regulator receiver domain, Sigma54 activation = central ATPase that interacts with σ54, HTH_8 = DNA-binding helix-turn-helix, Protoglobin = putative heme binding sensor domain, HisKA = domain of histidine phosphorylation and SK dimerization, HK CA:9 = ATPase. All domain nomenclatures are based on the Mist 2.2 database [87] and Pfam (http://pfam.xfam.org, [93]). The strain designation (C1-C9) is the same as in Table 1 and Fig 1.