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- Perez Boerema, Annemarie, 1991-
(författare)
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Cryo-EM Studies of Macromolecular Complexes from Photosynthetic Organisms
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Plants, algae, and cyanobacteria convert light energy into chemical energy through the process of photosynthesis, fueling the planet and making life as we know it possible. Photosystem I (PSI) is one of the main photosynthetic complexes, responsible for this process. PSI uses the energy of light to transfer electrons from the soluble electron carrier plastocyanin, on the lumenal site of the thylakoid membrane, to ferrodoxin, on the stromal site of the membrane. Thus, playing a key role in the light dependent reactions. In order to survive many photosynthetic organisms need to be able to adapt to fluctuations in light and have adapted their photosynthetic machinery accordingly. In recent years many advances have been made in electron cryo-microscopy, making it possible to visualize many previously elusive photosynthetic complexes. This has brought a wealth of information on the structural adaptations of PSI.In plants and algae, PSI is hosted by the chloroplast, a specialized organelle that houses the photosynthetic reactions. In the chloroplast, key components of PSI are synthesized by the chloroplasts own translation machinery: the chloroplast ribosome. Translation in the chloroplast is remarkable as it has to synchronize translation in two different genetic compartments as well as adapt to fluctuations in light. A glimpse of how this machinery has evolved to be able to fulfill all of these duties can be obtained from its three dimensional structure and its chloroplast specific features. However, despite all this structural information providing valuable clues as to the functioning of these systems, there are still many aspects of how they play a role that still remain unknown.
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| 2. |
- Singh, Vivek, 1988-
(författare)
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Structural investigation of human mitochondrial translation and off-target antibiotic binding
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Human mitochondrial translation machinery has evolved to translate 13 mitochondrial mRNAs encoding components of the oxidative phosphorylation pathway responsible for ATP production. The structural basis of human mitochondrial translation is distinct from the canonical bacterial and cytosolic translation systems. Further, mutations affecting mitochondrial protein synthesis disrupt ATP production resulting in myopathies and neurodegenerative diseases. Structural studies have identified the core components of the human mitoribosome and some of its associated translation factors but several important aspects such as the role of mito-specific proteins in translation, rRNA modifications, composition of its ultrastructure including ions, small molecule co-factors, and solvent content, remain poorly understood. Importantly, several important antibiotics that target bacterial translation also affect mitochondrial translation, thereby causing adverse effects in patients. Understanding the mechanism of off-target antibiotic binding to the mitoribosome could help in designing better antibiotics. In this work, we use electron cryo-microscopy to determine the structures of the human mitoribosome in complex with ligands: mRNA/tRNA and translation activators such as LRPPRC-SLIRP. This allows us to explore the structural basis of mitochondrial translation, identifying the roles of mito-specific protein elements in tRNA and mRNA binding and recruitment (Papers 1 and 2). We determine a 2.2 Å resolution structure of the human mitoribosome and a 2.4 Å resolution structure of the mitoribosomal small subunit in complex with the tuberculosis drug, streptomycin. Together, the structures represent the most detailed and complete models for the human mitoribosome, revealing rRNA and protein modifications; several novel small molecule cofactors: 2Fe-2S clusters, polyamines and nucleotides and mechanisms of antibiotic binding (Papers 3 and 4).
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| 3. |
- Tobiasson, Victor, 1994-
(författare)
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On the Origin and Evolution of the Mitochondrial Ribosome
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The ribosome is among the most ancient, intricate and well studied macromolecular complexes in biology. Predating the earliest divergence of life, its core molecular structure has remained mostly unchanged for more than three billion years. In stark contrast to its monolithic ancestor, the mitochondrial ribosome represents one of the most architecturally diverse protein complexes investigated. This work is an attempt at reconciling these two paradigms. In this thesis I first briefly cover the evolutionary history of the mitochondrial ribosome: from its ancient origins, through the process of Eukaryogenesis and the development of mitochondria, to its current state. Following this I present a comprehensive and integrated comparative analysis of the current mitoribosomal structures. Using these structural observations as a starting point I then summarise the current knowledge regarding the evolutionary trends of mitochondrial ribosomes. Finally I review and discuss potential genetic mechanisms and evolutionary pressures which could have produced such a vibrant diversity of structures. Together with this analysis I present monosome structures from the ciliate Tetrahymena thermophila and chlorophycean Polytomella magna together with an assembly intermediate of the large subunit from Trypanosoma brucei. Together, I hope to demonstrate the impact of the unique mitochondrial environment on the evolution of the mitochondrial ribosome.
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