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.
Haselkorn, Robert
Joachimiak, Andrzej
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Proceedings of the National Academy of Sciences of the United States of America
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 sitedirected mutagenesis and DNA-binding studies. We suggest that HetR serves as a scaffold for assembly of transcription components critical for heterocyst development.
Anabaena/Fischerella, HTH motifs, palindrome binding, patterned development
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