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CalA, a cyanobacterial AbrB protein, interacts with the upstream region of hypC and acts as a repressor of its transcription in the cyanobacterium Nostoc sp. strain PCC 7120
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Microbial Chemistry. (Peter Lindblad)
Department of Biological Sciences, Purdue University. (Louis Sherman)
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Microbial Chemistry. (Peter Lindblad)
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Microbial Chemistry. (Peter Lindblad)
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2010 (English)In: Applied and Environmental Microbiology, ISSN 0099-2240, E-ISSN 1098-5336, Vol. 76, no 3, 880-890 p.Article in journal (Refereed) Published
Abstract [en]

The filamentous, heterocystous, nitrogen-fixing cyanobacterium Nostoc sp. strain PCC 7120 may contain, depending on growth condition, up to two hydrogenases directly involved in hydrogen metabolism. HypC is one out of at least seven auxiliary gene products required for synthesis of a functional hydrogenase, specifically involved in the maturation of the large subunit. In this study we present a protein, Alr0946, belonging to the transcription regulator family AbrB, which in protein-DNA assays was found to interact with the upstream region of hypC. Transcriptional investigations showed that alr0946 is co-transcribed with the downstream gene alr0947, which encodes a putative protease from the abortive infection superfamily, Abi. Alr0946 was shown to interact specifically not only with the upstream region of hypC but also with its own upstream region, acting as a repressor on both. The bidirectional hydrogenase activity was significant down-regulated when Alr0946 was over-expressed demonstrating a correlation to the transcription factor, either direct or indirect. In silico studies showed that homologues to both Alr0946 and Alr0947 are highly conserved proteins within cyanobacteria with a very similar physical organisation of the corresponding structural genes. Possible functions of the co-transcribed downstream protein Alr0947 are presented. In addition, we present a 3D model of the CyAbrB domain of Alr0946 and putative DNA-binding mechanisms are discussed.

Place, publisher, year, edition, pages
2010. Vol. 76, no 3, 880-890 p.
Keyword [en]
Nostoc sp. strain PCC 7120, hypC, Alr0946, CyAbrB, hydrogen metabolism
National Category
Biological Sciences
Identifiers
URN: urn:nbn:se:uu:diva-110863DOI: 10.1128/AEM.02521-09ISI: 000274017400030OAI: oai:DiVA.org:uu-110863DiVA: diva2:278644
Available from: 2009-11-27 Created: 2009-11-27 Last updated: 2012-09-12
In thesis
1. Maturation and Regulation of Cyanobacterial Hydrogenases
Open this publication in new window or tab >>Maturation and Regulation of Cyanobacterial Hydrogenases
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Accelerated global warming plus an increasing need for energy is an equation not easily solved, thus new forms of sustainable energy production are urgently requested. In this context hydrogen production based on a cyanobacterial system offers an environmentally friendly alternative for energy capture and conversion. Cyanobacteria can produce hydrogen gas from sun light and water through the combination of photosystems and hydrogenases, and are suitable to cultivate in large scale.

In the present thesis the maturation process of [NiFe]-hydrogenases is investigated with special focus on transcription of the accessory genes encoding proteins needed for assembly of the large and possibly also for the small hydrogenase subunit. The cyanobacteria used are two N2-fixing, filamentous, heterocystous strains; Nostoc sp. strain PCC 7120 and Nostoc punctiforme PCC 73102.

For a biotechnological exploration of hydrogen production tools for regulatory purposes are important. The transcription factor CalA (cyanobacterial AbrB like) (Alr0946 in the genome) in Nostoc sp. strain PCC 7120 was found to be involved in hydrogen metabolism by regulating the transcription of the maturation protein HypC. Further the bidirectional hydrogenase activity was down-regulated in the presence of elevated levels of CalA, a result important to take into account when optimizing cyanobacteria for hydrogen production.

CalA regulates at least 25 proteins in Nostoc sp. strain PCC 7120 and one of the down-regulated proteins was superoxide dismutase, FeSOD. The characterization of FeSOD shows that it has a specific and important function in the oxidative stress tolerance of Nostoc sp. stain PCC 7120. Since CalA is involved in regulation of both the hydrogen metabolism as well as stress responses these findings indicate that Alr0946 is an important transcription factor in Nostoc sp. strain PCC 7120 active on a global level in the cell.

This thesis adds more knowledge concerning maturation and regulation of cyanobacterial hydrogenases which might be useful for future large scale hydrogen.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2009. 62 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 695
Keyword
Biohydrogen, Cyanobacteria, Nostoc sp. PCC 7120, Nostoc punctiforme PCC 73102, Hydrogenase, Maturation, Transcriptional regulation, CyAbrB, CalA, FeSOD
Identifiers
urn:nbn:se:uu:diva-110871 (URN)978-91-554-7673-1 (ISBN)
Public defence
2010-01-15, Häggsalen, The Ångström Laboratory, Lägerhyddsvägen 1, Polacksbacken, Uppsala, 13:00 (English)
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Available from: 2009-12-21 Created: 2009-11-27 Last updated: 2009-12-21Bibliographically approved

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Stensjö, KarinDevine, EllenorLindblad, Peter

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