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Functional Update of the Auxiliary Proteins PsbW, PsbY, HCF136, PsbN, TerC and ALB3 in Maintenance and Assembly of PSII
Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Chemistry.
Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Chemistry.
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2016 (English)In: Frontiers in Plant Science, ISSN 1664-462X, E-ISSN 1664-462X, Vol. 7, 423Article in journal (Refereed) PublishedText
Abstract [en]

Assembly of Photosystem (PS) II in plants has turned out to be a highly complex process which, at least in part, occurs in a sequential order and requires many more auxiliary proteins than subunits present in the complex. Owing to the high evolutionary conservation of the subunit composition and the three-dimensional structure of the PSII complex, most plant factors involved in the biogenesis of PSII originated from cyanobacteria and only rarely evolved de novo. Furthermore, in chloroplasts the initial assembly steps occur in the non-appressed stroma lamellae, whereas the final assembly including the attachment of the major LHCII antenna proteins takes place in the grana regions. The stroma lamellae are also the place where part of PSII repair occurs, which very likely also involves assembly factors. In cyanobacteria initial PSII assembly also occurs in the thylakoid membrane, in so-called thylakoid centers, which are in contact with the plasma membrane. Here, we provide an update on the structures, localisations, topologies, functions, expression and interactions of the low molecular mass PSII subunits PsbY, PsbW and the auxiliary factors HCF136, PsbN, TerC and ALB3, assisting in PSII complex assembly and protein insertion into the thylakoid membrane.

Place, publisher, year, edition, pages
2016. Vol. 7, 423
Keyword [en]
PSII photosystem II, cytochrome b559, assembly, low molecular mass proteins, Arabidopsis
National Category
Biochemistry and Molecular Biology
URN: urn:nbn:se:umu:diva-120622DOI: 10.3389/fpls.2016.00423ISI: 000373599400001PubMedID: 27092151OAI: diva2:953001
Available from: 2016-08-16 Created: 2016-05-18 Last updated: 2016-09-22Bibliographically approved
In thesis
1. Characterization of auxiliary membrane proteins in the chloroplast of Arabidopsis thaliana
Open this publication in new window or tab >>Characterization of auxiliary membrane proteins in the chloroplast of Arabidopsis thaliana
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Karakterisering av membran-lokaliserade hjälparproteiner i kloroplasten hos växten backtrav
Abstract [en]

In nature, sessile plants have to adapt to their environment and to the never ending changes they are exposed to. They do so mainly by proteomic and metabolomic changes. In all cells, there are complex networks of auxiliary proteins that are responsible for quality control of all the cell's proteins. The auxiliary proteins are divided into chaperones and proteases, and these are further separated into different groups. Chaperones help other proteins in terms of stability and folding. In order for a protein to achieve its function, the three-dimensional structure has to be precise. A protease is a helper protein that is able to break peptide bonds in a process termed proteolysis. Chaperones and proteases can work independently, but sometimes the chaperone unfolds the substrate of the protease to ensure full degradation of the protein. In some cases, the chaperone and the protease functions are combined in one protein.

All proteins studied within this thesis are localized in the chloroplast, the organelle that originated from cyanobacteria, in which plants and algae convert the energy from sunlight into carbohydrates in the process called photosynthesis. Molecular oxygen is released as a by-product, and carbon dioxide is consumed. Photosystem II (PSII), one of the major protein complexes involved in photosynthesis, consists of more than 30 protein subunits, where around half of them are termed low molecular weight (LMW) proteins with a molecular size less than 10 kDa. In this thesis, data identifying one PSII LMW protein, PsbY, as a chaperone for the PSII subcomplex Cytochrome b559 are presented. In the absence of PsbY, Arabidopsis plants were more sensitive to photoinhibition, and the protective circular electron transport around PSII is completely blocked.

Data on members of the Filamentation temperature sensitive protein H (FtsH) protease family are also discussed, with a focus on FtsH11 and FtsHi1-i5. Members of the FtsH protease family carry a protease domain and a chaperone domain. Our data show that FtsH11 has an influence on the structure and function of chloroplasts of Arabidopsis plants grown under continuous light along with protein import into the same. FtsHi1-5 are five members with mutations within the proteolytic motif, most probably rendering them proteolytically inactive, hence they are referred to as ''inactive FtsH proteases''. Knock-out plants of the inactive members are embryo lethal, and knock-down plants grow slower than wild type, probably because of an affected level of plastid proteins at the translational level.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2016. 52 p.
Arabidopsis, chaperone, chloroplast, Cytochrome b559, FtsH, membrane proteins, photosynthesis, Photosystem II, protease, PsbY., Arabidopsis, chaperone, Cytochrome b559, fotosyntes, fotosystem II, FtsH, kloroplast, membranprotein, proteas, PsbY.
National Category
Biochemistry and Molecular Biology Plant Biotechnology
Research subject
urn:nbn:se:umu:diva-125819 (URN)978-91-7601-480-6 (ISBN)
Public defence
2016-10-10, N450, Naturvetarhuset, Umeå, 10:00 (English)
Swedish Energy Agency, 2012-005889​

Avhandlingen är skriven på engelska, men innehåller också en enkel sammanfattning på svenska. 

Available from: 2016-09-26 Created: 2016-09-19 Last updated: 2016-09-23Bibliographically approved

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von Sydow, LottaSchröder, Wolfgang P.
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