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Transcription of the extended hyp-operon in Nostoc sp. strain PCC 7120
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.ORCID iD: 0000-0001-6993-8476
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
2008 (English)In: BMC Microbiology, ISSN 1471-2180, E-ISSN 1471-2180, Vol. 8, 69- p.Article in journal (Refereed) Published
Abstract [en]

Background: The maturation of hydrogenases into active enzymes is a complex process and e. g. a correctly assembled active site requires the involvement of at least seven proteins, encoded by hypABCDEF and a hydrogenase specific protease, encoded either by hupW or hoxW. The N2fixing cyanobacterium Nostoc sp. strain PCC 7120 may contain both an uptake and a bidirectional hydrogenase. The present study addresses the presence and expression of hypgenes in Nostoc sp. strain PCC 7120. Results: RTPCRs demonstrated that the six hypgenes together with one ORF may be transcribed as a single operon. Transcriptional start points (TSPs) were identified 280 bp upstream from hypF and 445 bp upstream of hypC, respectively, demonstrating the existence of several transcripts. In addition, five upstream ORFs located in between hupSL, encoding the small and large subunits of the uptake hydrogenase, and the hypoperon, and two downstream ORFs from the hypgenes were shown to be part of the same transcript unit. A third TSP was identified 45 bp upstream of asr0689, the first of five ORFs in this operon. The ORFs are annotated as encoding unknown proteins, with the exception of alr0692 which is identified as a NifUlike protein. Orthologues of the four ORFs asr0689alr0692, with a highly conserved genomic arrangement positioned between hupSL, and the hyp genes are found in several other N2fixing cyanobacteria, but are absent in non N2fixing cyanobacteria with only the bidirectional hydrogenase. Short conserved sequences were found in six intergenic regions of the extended hypoperon, appearing between 11 and 79 times in the genome. Conclusion: This study demonstrated that five ORFs upstream of the hypgene cluster are cotranscribed with the hypgenes, and identified three TSPs in the extended hypgene cluster in Nostoc sp. strain PCC 7120. This may indicate a function related to the assembly of a functional uptake hydrogenase, hypothetically in the assembly of the small subunit of the enzyme.

Place, publisher, year, edition, pages
2008. Vol. 8, 69- p.
National Category
Chemical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-110173DOI: 10.1186/1471-2180-8-69ISI: 000256297500001OAI: oai:DiVA.org:uu-110173DiVA: diva2:275501
Available from: 2009-11-05 Created: 2009-11-05 Last updated: 2017-12-12
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)
Opponent
Supervisors
Available from: 2009-12-21 Created: 2009-11-27 Last updated: 2009-12-21Bibliographically approved

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Stensjö, KarinHolmqvist, MarieLindblad, Peter

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