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Transcript analysis of the extended hyp-operons in the cyanobacteria Nostoc sp. strain PCC 7120 and Nostoc punctiforme ATCC 29133
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)
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Microbial Chemistry. (Peter Lindblad)ORCID iD: 0000-0001-6993-8476
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2011 (English)In: BMC Research Notes, ISSN 1756-0500, E-ISSN 1756-0500, Vol. 4, no 186Article in journal (Other academic) Published
Abstract [en]

The ability of cyanobacteria to capture solar energy, via oxygenic photosynthesis, and convert that energy to molecular hydrogen (H2) has made them an interesting group of organisms with potential as future energy producers. There are three types of enzymes directly involved in the cyanobacterial hydrogen metabolism; nitrogenases that produce H2 as a by-product when fixating atmospheric nitrogen, uptake hydrogenases that catalyze the oxidation of H2,thereby preventing energy losses from the cells, and bidirectional hydrogenases that has the capacity to both oxidize and reduce H2. Hydrogenases are complex metalloenzymes, and the insertion of ligands and correct folding of the proteins require assistance of accessory proteins, the Hyp proteins. Cyanobacterial hydrogenases are NiFe-type hydrogenases and consist of a large and a small subunit. Today, the maturation process of the large subunit has been uncovered to a large extent in cyanobacteria, mostly by analogy assumptions from studies done in other bacteria such as Escherichia coli but also from mutational analyses in cyanobacteria, while the maturation process of the small subunit is still unknown. Recently a set of genes, putatively involved in the maturation process of the small subunit, was discovered in Nostoc sp. PCC 7120 and Nostoc punctiforme ATCC 29133. These five ORFs, encoding unknown proteins, are located in between the uptake hydrogenase structural genes and the hyp-genes were shown to be transcribed together with the hyp-genes in Nostoc PCC 7120. The ORFs upstream the hyp-genes can be found in the same genomic arrangement in other filamentous, nitrogen fixing cyanobacterial strains but are interestingly missing in strains incapable of nitrogen fixation. In this study we have further investigated the function of the ORFs upstream the hyp-genes by studying their transcription pattern after nitrogen depletion in the filamentous, nitrogen fixing strains Nostoc PCC 7120 and N. punctiforme. The transcription pattern were compared to the transcription pattern of hupS and hoxY, encoding the uptake and bidirectional hydrogenase small subunits, nifD, encoding a nitrogenase subunit and hypC and hypF, encoding the maturation process accessory proteins HypC and HypF. All the five ORFs upstream the hyp-genes, in both organisms, were upregulated after nitrogen step down in accordance with the transcription pattern for hupS, nifD, hypC and hypF which support the theory that these genes might be involved in the maturation of the small subunit.

Place, publisher, year, edition, pages
London: BioMed Central, 2011. Vol. 4, no 186
Keyword [en]
Nostoc sp.strain PCC 7120, Nostoc punctiforme ATCC29133, hyp, hydrogenase maturation
National Category
Biochemistry and Molecular Biology
URN: urn:nbn:se:uu:diva-110865DOI: 10.1186/1756-0500-4-186OAI: oai:DiVA.org:uu-110865DiVA: diva2:278651
Available from: 2009-11-27 Created: 2009-11-27 Last updated: 2016-04-21
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.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 695
Biohydrogen, Cyanobacteria, Nostoc sp. PCC 7120, Nostoc punctiforme PCC 73102, Hydrogenase, Maturation, Transcriptional regulation, CyAbrB, CalA, FeSOD
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)
Available from: 2009-12-21 Created: 2009-11-27 Last updated: 2009-12-21Bibliographically approved

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