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HetF and PatA Control Levels of HetR in Anabaena sp. Strain PCC 7120

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Title: HetF and PatA Control Levels of HetR in Anabaena sp. Strain PCC 7120
Authors: Risser, Douglas D.
Callahan, Sean M.
Issue Date: Oct 2008
Publisher: American Society for Microbiology
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Abstract: Anabaena sp. strain PCC 7120 is a filamentous cyanobacterium that differentiates heterocysts in response to deprivation of combined nitrogen. A hetF deletion strain lacked heterocysts and had aberrant cell morphology. Site-directed mutagenesis of the predicted active-site histidine and cysteine residues of this putative caspasehemoglobinase fold protease abolished HetF function, supporting the hypothesis that HetF is a protease. Deletion of patA, which is necessary for the formation of most intercalary heterocysts, or hetF resulted in an increase in HetR protein, and extra copies of hetF on a plasmid functionally bypassed the deletion of patA. A hetR-gfp translational fusion expressed from an inducible promoter demonstrated that hetF-dependent downregulation of HetR levels occurs rapidly in vegetative cells, as well as developing heterocysts. “Mosaic” filaments in which only one cell of a filament had a copy of hetR or hetF indicated that hetF is required for differentiation only in cells that will become heterocysts. hetF was required for transcription from a hetRdependent transcription start point of the hetR promoter and induction of transcription from the patS promoter. The inverse correlation between the level of HetR protein and transcription from hetR-dependent promoters suggests that the transcriptional activity of HetR is regulated by HetF and PatA.
Pages/Duration: 10
DOI: 10.1128/JB.01110-08
Rights: Copyright © 2008, American Society for Microbiology. All Rights Reserved.
Appears in Collections:Department of Microbiology Faculty & Researcher Works

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