Structure of transcription factor HetR required for heterocyst differentiation in cyanobacteria.

Kim, Youngchang; Joachimiak, Grazyna; Ye, Zi; Binkowski, T Andrew; Zhang, Rongguang; Gornicki, Piotr; Callahan, Sean M; Hess, Wolfgang R et al. · Proc Natl Acad Sci U S A · 2011

basic_science · Level V

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Abstract

HetR is an essential regulator of heterocyst development in cyanobacteria. HetR binds to a DNA palindrome upstream of the hetP gene. We report the crystal structure of HetR from Fischerella at 3.0 Å. The protein is a dimer comprised of a central DNA-binding unit containing the N-terminal regions of the two subunits organized with two helix-turn-helix motifs; two globular flaps extending in opposite directions; and a hood over the central core formed from the C-terminal subdomains. The flaps and hood have no structural precedent in the protein database, therefore representing new folds. The structural assignments are supported by site-directed mutagenesis and DNA-binding studies. We suggest that HetR serves as a scaffold for assembly of transcription components critical for heterocyst development.

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