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. 2019 Aug 21;10:1923. doi: 10.3389/fmicb.2019.01923

FIGURE 1.

FIGURE 1

RpoSBb (BB0771) is a divergent RpoS that retains residues and structural features important for RpoS function and promoter selectivity. (A) Overlay of RpoSEc structure (PDB: 5IPL-F) (Liu et al., 2016) and RpoSBb homology model. Indicated are conserved isoleucine (I128 and I79 in RpoSEc and RpoSBb, respectively) (Iwase et al., 2017) and positively charged residues (K173 in RpoSEc and R121 and K122 in RpoSBb) (Barne et al., 1997) known or predicted to be important for promoter selectivity by RpoS. The C-terminal domain (CTD, residues 315–330 in RpoSEc) conserved in RpoS homologs from γ-proteobacteria is indicated (Liu et al., 2016). (B) Functional subdomains in the RpoSBb homology model were defined according to the corresponding regions in RpoSEc (Lonetto et al., 1992) using the aligned structures in panel A. (C–F) Electrostatic distribution in RpoSEc (C), RpoSBb homology model (D), RpoDEc (PDB: 6CY9) (E), and RpoDBb (BB0712) homology models (F). The negatively charged glutamic acid residue (E458 in RpoDEc and E474 in RpoDBb) in σ region 3.1 used to distinguish between RpoD (σ70) housekeeping and RpoS σ factors (Barne et al., 1997) is indicated.