6dxo

Publication Abstract from PubMed

Streptomyces are filamentous bacteria with a complex developmental life cycle characterized by the formation of spore-forming aerial hyphae. Transcription of the chaplin and rodlin genes, which are essential for aerial hyphae production, is directed by the extracytoplasmic function (ECF) sigma factor BldN, which is in turn controlled by an anti-sigma factor, RsbN. RsbN shows no sequence similarity to known anti-sigma factors and binds and inhibits BldN in an unknown manner. Here we describe the 2.23 A structure of the RsbN-BldN complex. The structure shows that BldN harbors sigma2 and sigma4 domains that are individually similar to other ECF sigma domains, which bind -10 and -35 promoter regions, respectively. The anti-sigma RsbN consists of three helices, with alpha3 forming a long helix embraced between BldN sigma2 and sigma4 while RsbN alpha1-alpha2 dock against sigma4 in a manner that would block -35 DNA binding. RsbN binding also freezes BldN in a conformation inactive for simultaneous -10 and -35 promoter interaction and RNAP binding. Strikingly, RsbN is structurally distinct from previously solved anti-sigma proteins. Thus, these data characterize the molecular determinants controlling a central Streptomyces developmental switch and reveal RsbN to be the founding member of a new structural class of anti-sigma factor.

The crystal structure of the RsbN-sigmaBldN complex from Streptomyces venezuelae defines a new structural class of anti-sigma factor.,Schumacher MA, Bush MJ, Bibb MJ, Ramos-Leon F, Chandra G, Zeng W, Buttner MJ Nucleic Acids Res. 2018 Jun 14. pii: 5037724. doi: 10.1093/nar/gky493. PMID:29905823^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.