ECF26

ECF subgroups

ECF26s1 524 ECF26s2 293 ECF26s3 270 ECF26s4 277 ECF26s5 177 ECF26s6 166 ECF26s7 166 ECF26s8 124 ECF26s9 112 ECF26s10 96 ECF26s11 98 ECF26s12 117 ECF26s13 110 ECF26s14 64 ECF26s15 49 ECF26s16 73 ECF26s17 54 ECF26s18 75 ECF26s19 43 ECF26s20 53 ECF26s21 124 ECF26s22 60 ECF26s23 50 ECF26s24 54 ECF26s25 41 ECF26s26 30 ECF26s27 27 ECF26s28 27 ECF26s29 24 ECF26s30 16 ECF26s31 23 ECF26s32 22 ECF26s33 50 ECF26s34 15 ECF26s35 23 ECF26s36 62 ECF26s37 26 ECF26s38 8 ECF26s39 13 ECF26s40 16 ECF26s41 17 ECF26s42 19 ECF26s43 12 ECF26s44 17 ECF26s45 20 ECF26s46 8 ECF26s47 6 ECF26s48 10 ECF26s49 6 ECF26s50 11 ECF26s51 3 ECF26s52 8 ECF26s53 12

ECF proteins

General description: Proteins from ECF26 have homology to proteins from the original group ECF26 (94.35%). Group ECF26 is present in Proteobacteria (99.87%), mainly Alpha- and Betaproteobacteria, and Bacteroidetes (0.13%) from genus Bacteroides.

Anti-σ factor: Members of ECF26 contain a putative AS factor in position +1, as described for the original group ECF26 (Staroń et al., 2009). Putative AS factors of ECF26 contain one TM helix (85.83%) and a zinc finger.

Genomic context conservation: Position -1 is usually conserved, and its specific function depends on the position of the subgroup in the phylogenetic tree of ECF26; we could find catalases (ECF26s1), subtilases (ECF26s10, ECF26s4, ECF26s27 and ECF26s14), chitin-binding proteins (ECF26s2), enoyl-(acyl carrier protein) reductases involved in fatty acid biosynthesis (ECF26s12), and a conserved protein with a secreted repeat domain (ECF26s6, ECF26s16, ECF26s17 and ECF26s9). Other domains conserved in the context of members of ECF26 are the SsrA-system RNA-binding protein SmpB (ECF26s9), the domain of the inhibitor of apoptosis-promoting Bax1 involved in calcium leakage across the membrane (ECF26s7 and ECF26s22), the prokaryotic cytochrome b561 from the electron transport chain (ECF26s1), a LysR-like transcription regulator (ECF26s8), the small subunit of an acetolactate synthase (ECF26s6), the beta subunit of the nitrile hydratase (ECF26s6), an aldo/keto reductase (ECF26s6), an UvrD-like helicase (ECF26s6), a LysE type translocator (ECF26s6), a DUF1194-containing protein (ECF26s12), a 17 kDa outer membrane surface antigen (ECF26s12), a pyridoxine 5'-phosphate oxidase (ECF26s12), a histidine phosphatase (ECF26s12), a chorismate synthase  (ECF26s12), a DnaJ-like protein (ECF26s12), an ubiquitin from the RnfH family (ECF26s9), an IMP dehydrogenase/GMP reductase (ECF26s9) and a polyketide cyclase/dehydrase (ECF26s9).

Studied members: SigE from Starkella novella (ECF26s28) regulates the expression of sorAB, located in +2 and +3, which encode a soluble sulfite:cytochrome c oxidoreductase involved in thiosulfate oxidation independent of a membrane-associated thiosulfate-oxidizing complex during chemolithotrophy (Kappler, Friedrich, Trüper, & Dahl, 2001). The protein encoded downstream of SigE has been proposed to be a membrane-bound AS factor with a short cytoplasmic region (Kappler et al., 2001). PrtI (ECF26s1), present in Pseudomonas spp., regulates the temperature-dependent production of a protease in P. fluorescens WH6 (Okrent et al., 2014). Sinorhizobium meliloti encodes four members of ECF26, RpoE1 (ECF26s6), RpoE3 (ECF26s29), RpoE4 (ECF26s34) and RpoE6 (ECF26s14). RpoE1 and RpoE4 are involved in detoxification of disulfide compounds, and all are regulated by one transmembrane helix AS factors encoded in +1 (Lang et al., 2018)., and all are regulated by one transmembrane helix AS factors encoded in +1 (Lang et al., 2018).

Promoter motif conservation: The promoter motifs are diverse but usually follow the pattern GGAATAAA in -35 and GTT in -10 in agreement with previous reports (Rhodius et al., 2013). This conservation indicates the autoregulatory role of members of ECF26. Indeed, SigE from S. novella is self-induced, although its described promoter motif (Kappler et al., 2001) does not entirely agree with the predicted target promoter of ECF26. ECFs from group ECF26 in S. meliloti are autoregulated (except RpoE3), and their binding motif agrees with the predictions for ECF26, although the specific predicted target promoter motifs of their subgroups might vary (Lang et al., 2018).