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Cyanobacterial hydrogenases: diversity, regulation and applications
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
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2007 (English)In: FEMS Microbiology Reviews, ISSN 0168-6445, E-ISSN 1574-6976, Vol. 31, no 6, 692-720 p.Article, review/survey (Refereed) Published
Abstract [en]

Cyanobacteria may possess two distinct nickel-iron (NiFe)-hydrogenases: an uptake enzyme found in N2-fixing strains, and a bidirectional one present in both non-N2-fixing and N2-fixing strains. The uptake hydrogenase (encoded by hupSL) catalyzes the consumption of the H2 produced during N2 fixation, while the bidirectional enzyme (hoxEFUYH) probably plays a role in fermn. and/or acts as an electron valve during photosynthesis. HupSL constitute a transcriptional unit, and are essentially transcribed under N2-fixing conditions. The bidirectional hydrogenase consists of a hydrogenase and a diaphorase part, and the corresponding five hox genes are not always clustered or cotranscribed. The biosynthesis/maturation of NiFe-hydrogenases is highly complex, requiring several core proteins. In cyanobacteria, the genes that are thought to affect hydrogenases pleiotropically (hyp), as well as the genes presumably encoding the hydrogenase-specific endopeptidases (hupW and hoxW) have been identified and characterized. Furthermore, NtcA and LexA have been implicated in the transcriptional regulation of the uptake and the bidirectional enzyme resp. Recently, the phylogenetic origin of cyanobacterial and algal hydrogenases was analyzed, and it was proposed that the current distribution in cyanobacteria reflects a differential loss of genes according to their ecol. needs or constraints. In addn., the possibilities and challenges of cyanobacterial-based H2 prodn. are addressed.

Place, publisher, year, edition, pages
2007. Vol. 31, no 6, 692-720 p.
Keyword [en]
cyanobacteria, hydrogenase, hup, hox, hyp, transcriptional regulator
National Category
Chemical Sciences
URN: urn:nbn:se:uu:diva-12242DOI: 10.1111/j.1574-6976.2007.00085.xISI: 000250297800004PubMedID: 17903205OAI: oai:DiVA.org:uu-12242DiVA: diva2:40011
Available from: 2007-12-07 Created: 2007-12-07 Last updated: 2011-03-29Bibliographically approved
In thesis
1. Regulation of the Cyanobacterial Bidirectional Hydrogenase
Open this publication in new window or tab >>Regulation of the Cyanobacterial Bidirectional Hydrogenase
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Today, mankind faces a new challenge in energetic terms: a new Industrial Revolution is imperative, already called by some as an Energetic Revolution. This corresponds to a conversion to clean, environmentally friendly and renewable energy sources. In this context, hydrogen arises as a valid alternative, since its combustion produces a considerable amount of energy and releases solely water as a by-product. In the present thesis, two model cyanobacteria, namely Synechocystis sp. strain PCC 6803 and Anabaena/Nostoc sp. strain PCC 7120, were used to examine the hydrogen metabolism. The efforts were focused on to understand the transcription regulation of the hox genes, encoding the structural elements of the bidirectional hydrogenase enzyme. Here, it is shown that such regulation is operated in a very distinct and intricate way, with different factors contributing to its delicate tuning. While in Synechocystis sp. strain PCC 6803 the hox genes were shown to be transcribed as a single operon, in Anabaena/Nostoc sp. strain PCC 7120 they were shown to be transcribed as two independent operons (possibly three). Two transcription factors, LexA and AbrB-like protein, were identified and further characterized in relation to the hydrogen metabolism. Furthermore, different environmental conditions were demonstrated to operate changes on the transcription of the bidirectional hydrogenase genes. In addition, functional studies of three open reading frames found within the hox operon of Synechocystis sp. strain PCC 6803 suggest that this may be a stress responsive operon. However, based on the gained knowledge, it is still not possible to connect the signal transduction pathways, from the environmental signal, through the response regulator, to the final regulation of the hox genes. Nevertheless, the crucial importance of studying the transcription regulation of the different players involved in the hydrogen metabolism is now established and a new era seems to be rising.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2008. 63 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 437
Biology, Biohydrogen, Cyanobacteria, Synechocystis, Anabaena/Nostoc, Bidirectional hydrogenase, Transcription regulation, LexA, AbrB-like protein, Biologi
urn:nbn:se:uu:diva-8862 (URN)978-91-554-7215-3 (ISBN)
Public defence
2008-06-05, Å2001, The Ångström Laboratory, Lägerhyddsvägen 1, Polacksbacken,, Uppsala, 10:15 (English)
Available from: 2008-05-14 Created: 2008-05-14 Last updated: 2009-08-17Bibliographically approved

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