In higher plants, [2Fe-2S] cluster containing fererdoxins (Fds) are the unique electron acceptors from photosystem I (PSI). Fds are small, soluble proteins and distribute these electrons to many enzymes, which act in different metabolic and signaling pathways. In addition to four well studied Fds, Arabidopsis possess genes for two significantly different, as yet uncharacterized Fds, with extended C-terminals, which are therefore called FdCs. For normal Fds, this C-terminus is critical for interaction with the C, D and E subunits of PSI during photosynthetic electron transport (PET). FdC1 and FdC2 are highly conserved from algae and cyanobacteria respectively to higher plants. This leads to the suggestion that they fulfill a conserved function, which is so far unknown. The results presented in this thesis show that FdC1 is a chloroplast located protein with a [2Fe-2S] cluster showing a blue shift in the electron paramagnetic resonance (EPR) spectrum in comparison to the well-known Fds. The EPR g values of FdC1 point to high similarity with the organization of the succinate dehydrogenase [2Fe-2S] cluster than that of classical Fd clusters. Furthermore it was established that FdC1 is unlikely to be involved in PET, due to its inability to photoreduce NADP+, because of a more positive redox potential in comparison to the well-studied Fds. In several interaction studies no previously described Fd-dependent enzymes could be found. By contrast FdC1 was found to interact with two of five enzymes of sulfate assimilation, serine O-acetyltransferase 2;1 (SERAT2;1) and 3‘-phosphoadenosine 5‘-phosphosulfate synthase (APS3), and it is proposed that FdC1 might have a regulatory function in sulfur assimilation through its interaction with these two proteins. Furthermore, several redox enzymes were found to interact with FdC1. One of these enzymes is the 3-oxoacyl-[acyl-carrier-protein] reductase, which is part of the fatty acid synthase complex. This interaction opens up the question, whether FdC1 might be able to channel electrons into the synthesis of specific fatty acids. In case of FdC2 the results have also proven that it is a chloroplast located protein containing a [2Fe-2S] cluster. FdC2 was detected in defined foci in the chloroplast, and our data suggests that in is both soluble and localized at the chloroplast envelope membrane. FdC2 is also very unlikely to be involved in PET, because it was found to be unable to receive electrons from PSI or FNR. Furthermore it is proposed that FdC2 has an alternative function in copper (Cu) import into the chloroplast through interaction with a Cu transporting ATPase, PAA1. This interaction was confirmed by several methods, although its functional significance is not yet completely understood. One possibility is that FdC2 regulates PAA1 or supports the reduction of Cu2+ to Cu+, before import into the chloroplast is possible.
| Identifer | oai:union.ndltd.org:uni-osnabrueck.de/oai:repositorium.ub.uni-osnabrueck.de:urn:nbn:de:gbv:700-2014022612281 |
| Date | 26 February 2014 |
| Creators | Goss, Tatjana |
| Contributors | PD Guy T. Hanke, Prof. Dr. Renate Scheibe |
| Source Sets | Universität Osnabrück |
| Language | English |
| Detected Language | English |
| Type | doc-type:doctoralThesis |
| Format | application/pdf, application/zip |
| Rights | Attribution-NonCommercial-NoDerivatives 4.0 International, http://creativecommons.org/licenses/by-nc-nd/4.0/ |
Page generated in 0.0025 seconds