title: Structures of complexes comprised of Fischerella transcription factor HetR with Anabaena DNA targets.
abstract: HetR is an essential regulator of heterocyst development in cyanobacteria. Many mutations in HetR render Anabaena incapable of nitrogen fixation. The protein binds to a DNA palindrome upstream of hetP and other genes. We have determined the crystal structures of HetR complexed with palindromic DNA targets, 21, 23, and 29 bp at 2.50-, 3.00-, and 3.25-Å resolution, respectively. The highest-resolution structure shows fine details of specific protein-DNA interactions. The lower-resolution structures with longer DNA duplexes have similar interaction patterns and show how the flap domains interact with DNA in a sequence nonspecific fashion. Fifteen of 15 protein-DNA contacts predicted on the basis of the structure were confirmed by single amino acid mutations that abolished binding in vitro and complementation in vivo. A striking feature of the structure is the association of glutamate 71 from each subunit of the HetR dimer with three successive cytosines in each arm of the palindromic target, a feature that is conserved among all known heterocyst-forming cyanobacteria sequenced to date.
authors.affiliation: Midwest Center for Structural Genomics and Structural Biology Center, Biosciences, Argonne National Laboratory, Argonne, IL 60439, USA.
authors.forename: Youngchang
authors.initials: Y
authors.lastname: Kim
authors.forename: Zi
authors.initials: Z
authors.lastname: Ye
authors.forename: Grazyna
authors.initials: G
authors.lastname: Joachimiak
authors.forename: Patrick
authors.initials: P
authors.lastname: Videau
authors.forename: Jasmine
authors.initials: J
authors.lastname: Young
authors.forename: Kathryn
authors.initials: K
authors.lastname: Hurd
authors.forename: Sean M
authors.initials: SM
authors.lastname: Callahan
authors.forename: Piotr
authors.initials: P
authors.lastname: Gornicki
authors.forename: Jindong
authors.initials: J
authors.lastname: Zhao
authors.forename: Robert
authors.initials: R
authors.lastname: Haselkorn
authors.forename: Andrzej
authors.initials: A
authors.lastname: Joachimiak
mesh_terms: D000596:Amino Acids / Q000737:chemistry; D017033:Anabaena / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D018360:Crystallography, X-Ray; D000458:Cyanobacteria / Q000235:genetics* / Q000378:metabolism; D003596:Cytosine / Q000737:chemistry; D004269:DNA, Bacterial / Q000737:chemistry*; D005816:Genetic Complementation Test; D018698:Glutamic Acid / Q000737:chemistry; D055029:Inverted Repeat Sequences; D008958:Models, Molecular; D008968:Molecular Conformation; D016296:Mutagenesis; D009154:Mutation; D009584:Nitrogen / Q000737:chemistry; D011485:Protein Binding; D017422:Sequence Analysis, DNA; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: D000596:Amino Acids; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D014157:Transcription Factors; C067403:HetR protein, Bacteria; D018698:Glutamic Acid; D003596:Cytosine; D009584:Nitrogen
keywords: X-ray crystallography; heterocyst differentiation; mutagenesis