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Proteomic approaches to identify substrates of the three Deg/HtrA proteases of the cyanobacterium Synechocystis sp. PCC 6803
Umeå University, Faculty of Science and Technology, Department of Chemistry.
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(English)Article in journal (Refereed) Submitted
National Category
Organic Chemistry
URN: urn:nbn:se:umu:diva-99838OAI: diva2:788279
Available from: 2015-02-13 Created: 2015-02-13 Last updated: 2015-02-16
In thesis
1. Deg/HtrA proteases of the cyanobacterium Synechocystis sp. PCC 6803: from biochemical characterization to their physiological functions
Open this publication in new window or tab >>Deg/HtrA proteases of the cyanobacterium Synechocystis sp. PCC 6803: from biochemical characterization to their physiological functions
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The family of Deg/HtrA proteases is present in a wide range of organisms from bacteria, archaea to eukaryota. These ATP-independent serine endopeptidases play key roles in the cellular protein quality control. The cyanobacterium Synechocystis sp. PCC 6803, a model organism for studies on photosynthesis, metabolism and renewable energy, contains three Deg proteases known as HhoA, HhoB and HtrA. The three proteases are important for survival in stress conditions, such as high light or temperature.

In my work the biochemical characteristics of each protease were revealed in vitro and in vivo. In vitro studies performed using recombinant Synechocystis Deg proteases allowed conclusions about their oligomerization states, proteolytic activities and tertiary structure. The in vivo studies addressed their sub-cellular localization, expression and physiological importance by comparing wild-type Synechocystis cells with the three single mutants lacking one of the Deg proteases.

HhoA seems to be involved in the cytoplasmic protein quality control. This protease is regulated post-transcriptional and post-translational: oligomerization, pH and/or cation-binding are some of the important factors to stimulate its proteolytic activity. Instead HhoB acts on periplasmic proteins and seems to be important for the transportation/secretion of proteins. While it has low proteolytic capacity, it may act as a chaperone. The stress-induced HtrA functions in the cellular tolerance against photosynthetic stress; additionally it might act as a protease partner of HhoB, generating a protease/chaperone complex.

The results presented in this thesis lay the foundation for a better understanding of the dynamic protein quality control in cyanobacteria, which is undoubtedly important for various cellular metabolic pathways.

Place, publisher, year, edition, pages
Umeå: Umeå University, 2015. 35 p.
Deg, HtrA, protease, chaperone, Synechocystis sp. PCC 6903, biochemical characterization, physiological function, proteomics, structure
National Category
Biochemistry and Molecular Biology
urn:nbn:se:umu:diva-99719 (URN)978-91-7601-223-9 (ISBN)
Public defence
2015-03-16, KB3A9, KBC building, Umeå University, Umeå, 10:00 (English)
Available from: 2015-02-23 Created: 2015-02-12 Last updated: 2015-03-06Bibliographically approved

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Lâm, Xuân TâmFunk, Christiane
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