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Arch Microbiol. 2010 Jun;192(6):461-9. doi: 10.1007/s00203-010-0573-9. Epub 2010 Apr 20.

CalA, a cyAbrB protein, binds to the upstream region of ftsZ and is down-regulated in heterocysts in Anabaena sp. PCC 7120.

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The State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, 430072, Wuhan, Hubei, China.


A protein of cyAbrB family of regulators, Alr0946 (CalA), was identified by DNA affinity chromatography using DNA fragments from the promoter region of ftsZ in Anabaena/Nostoc sp. PCC 7120. Electrophoretic mobility shift assays showed that the protein could bind to upstream regions of ftsZ (as biotin-labeled DNA fragments) and that the binding was inhibited by the same DNA fragments and a fragment upstream of hetC but not by 3 fragments upstream of glnA, hetR or ntcA. Both transcriptional fusion with gfp (green fluorescence protein) and Western blot analysis indicated that the expression of calA was down-regulated in heterocysts relative to vegetative cells. An insertional mutant of calA could not be completely segregated. Over-expression of calA in Anabaena/Nostoc caused no change in growth, heterocyst differentiation or expression of ftsZ. CalA as a DNA-binding protein is essential for the growth of Anabaena/Nostoc and may be required for the expression of ftsZ in vegetative cells.

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