Portal de Periódicos da CAPES

Characterization of a protein–protein interaction within the SigO–RsoA two-subunit σ factor: the σ70 region 2.3-like segment of RsoA mediates interaction with SigO

2016; Microbiology Society; Volume: 162; Issue: 10 Linguagem: Inglês

10.1099/mic.0.000358

1465-2080

Xiaowei Xue, Maria C. Davis, Thomas Steeves, A. R. Bishop, Jillian Breen, Allison MacEacheron, Christopher A. Kesthely, FoSheng Hsu, Shawn R. MacLellan,

Antibiotic Resistance in Bacteria

σ factors are single subunit general transcription factors that reversibly bind core RNA polymerase and mediate gene-specific transcription in bacteria. Previously, an atypical two-subunit σ factor was identified that activates transcription from a group of related promoters in Bacillus subtilis. Both of the subunits, named SigO and RsoA, share primary sequence similarity with the canonical σ70 family of σ factors and interact with each other and with RNA polymerase subunits. Here we show that the σ70 region 2.3-like segment of RsoA is unexpectedly sufficient for interaction with the amino-terminus of SigO and the β' subunit. A mutational analysis of RsoA identified aromatic residues conserved amongst all RsoA homologues, and often amongst canonical σ factors, that are particularly important for the SigO-RsoA interaction. In a canonical σ factor, region 2.3 amino acids bind non-template strand DNA, trapping the promoter in a single-stranded state required for initiation of transcription. Accordingly, we speculate that RsoA region 2.3 protein-binding activity likely arose from a motif that, at least in its ancestral protein, participated in DNA-binding interactions.