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Proteins involved in the tetrapyrrole pathway in Synechocystis sp. PCC 6803 and their localization in the proximity of PSII biogenesis
SKOTNICOVÁ, Petra
The goal of the thesis was to enhance our understanding of the tetrapyrrole pathway in cyanobacteria by a study of selected proteins involved in the pathway. During the project I have revealed functional connection between protoporphyrinogen IX oxidase HemJ and preceding enzyme in the pathway by complementation of protoporphyrinogen IX oxidase deletion mutant by its analog HemG from Escherichia coli. Heme b was identified as a cofactor of HemJ. Another protein deeply influencing tetrapyrrole accumulation, BtpA was found to form a complex with GluTR, the enzyme at the beginning of the tetrapyrrole pathway. Lastly, CurT protein, the component of the structures anticipated to function in PSII assembly and/or repair localized at plasma/thylakoid membrane interface, was co isolated with the enzymes of the tetrapyrrole pathway suggesting that the specific CurT containing membranes could be a place of both photosystem II assembly/repair and chlorophyll delivery.
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Function of the Type IV pili proteins in the cyanobacterium Synechocystis sp. PCC 6803.
LINHARTOVÁ, Markéta
The thesis is focused on the function of the Type IV pili machinery in the cyanobacterium Synechocystis sp. PCC. 6803. In my work, I provided evidence that in phototrophs, some pilin proteins have acquired a novel function related to metal transport and assembly of photosynthetic complexes. The tight connection between the synthesis of the major pilin PilA1 and the biogenesis of photosynthetic complexes has been demonstrated in the pilD mutant lacking prepilins peptidase. I isolated and characterized pilD suppressor strains, which revealed the important role of the minor pilin PilA2 in the glycosylation of PilA1 and the restricted mobility of PilA1 prepilin in the membrane. My unpublished data indicate that the retraction mode of pili, driven by the PilT1 molecular motor, facilitates manganese uptake and the activity of this machine is critically important during the regulation from the exponential to the linear growth phase.
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Role of Psb28 proteins in the biogenesis of the Photosystem II complex in the cyanobacterium Synechocystis sp. PCC 6803
BEČKOVÁ, Martina
The thesis focuses on the role of Psb28 proteins, namely the Psb28-1 and its homolog Psb28-2, in the biogenesis of the Photosystem II complex (PSII) in the cyanobacterium Synechocystis PCC 6803. The aims of this work were to localize the proteins within the cells, and to determine their function. A fraction of both Psb28 proteins was identified in the monomeric PSII core complexes but most proteins were found in the unassembled protein fraction associated with thylakoid membranes. Psb28-1 was mostly detected as a dimer while Psb28-2 as a monomer. Psb28-1 also differed from Psb28-2 by its higher affinity to the PSII core complex lacking CP43 antenna. Characterization of Psb28-less mutants suggested regulatory function of the proteins in PSII biogenesis in connection with chlorophyll biosynthetic pathway. Analysis of preparations isolated using FLAG-tagged versions of Psb28 proteins showed their association with Photosystem II - Photosystem I supercomplexes, especially under increased irradiance, and supported a role of Photosystem I in the PSII biogenesis.
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Biogenesis of Photosystem II in the Model Cyanobacterium Synechocystis sp. PCC 6803 - The Role of Selected Auxiliary Protein Factors and Subcellular Localisation
KNOPPOVÁ, Jana
This thesis explores localisations and roles of three auxiliary protein factors involved in the biogenesis of Photosystem II (PSII) in the cyanobacterium Synechocystis sp. PCC 6803 and contributes to subcellular localisation of the initial steps of PSII biogenesis and repair-related D1 synthesis. The main results consist in i) identification of a functional interaction of the protein factor Psb27 with a lumenal domain of the Photosystem II subunit CP43, ii) discovery of a novel pigment binding complex formed by the Ycf39 protein and high-light-inducible proteins implicated in photoprotection and delivery of recycled chlorophyll to newly synthesized D1 protein during the PSII reaction centre formation, iii) providing evidence that the early steps of PSII assembly and the repair-related D1 synthesis occur in the thylakoid membrane of Synechocystis, and iv) revealing that the cyanobacterial PsbP orthologue, CyanoP, assists in the early phase of PSII biogenesis as an assembly factor facilitating the association of D2 and D1 assembly modules.
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Role of FtsH proteases in the cyanobacterium Synechocystis sp. PCC 6803
KRYNICKÁ, Vendula
This thesis focuses on the functional and structural characterization of FtsH proteases in Synechocystis PCC 6803. One of the aims was to determine localization and subunit organization of FtsH homologues in Synechocystis cells using GST and GFP tagged FtsH derivatives. The main result of the thesis is identification of two FtsH hetero-oligomeric complexes and one homo-oligomeric complex in Synechocystis cells. The large part of the thesis is aimed at establishing the role of the first hetero-oligomeric complex, FtsH2/FtsH3, in quality control of Photosystem II and at identification of a mechanism, how its substrate proteins D1 and D2 are recognized. Another part is dedicated to characterization of the second hetero-oligomeric complex, FtsH1/FtsH3, which consists of two essential FtsH homologues and which is here identified as an important regulatory element in maintaining iron homeostasis.
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Construction of expression vector for cyanobacterium \kur{Synechocystis} sp. PCC 6803
RICHTOVÁ, Jitka
The cyanobacterium Synechocystis sp. PCC 6803 is an important model organism used in the study of photosynthesis and related processes. The only disadvantage of Synechocystis for molecular biology studies is that it lacks a cloning/expression system. The aim of this work was to evaluate whether it is possible to use a mutated high copy version of the native Synechocystis plasmid for expression of a chosen gene in this organism.
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