Project description
Not all ribosomes are created equal
Mitochondria and chloroplasts are cellular organelles that play a role in the energy pathway. Mitochondria are found in both plants and animals and are the so-called powerhouses of cells, breaking down nutrients (primarily glucose) to make energy in the form of adenosine triphosphate (ATP). However, animals get their energy-rich nutrients by ingesting them, whereas plants make their glucose via photosynthesis in the plants' chloroplasts. Both mitochondria and chloroplasts likely have bacterial ancestors that developed symbiotic relationships with host cells and eventually became the organelles we know today. Both have their own machinery to make proteins including DNA and ribosomes, but we still do not know a lot about the ribosomes in mitochondria and chloroplasts. The EU-funded Orgasome project plans to get an experimental 'time-lapse' reconstruction of translation in these two organelles to get to the bottom of things.
Objective
Protein synthesis in mitochondria is essential for the bioenergetics, whereas its counterpart in chloroplasts is responsible for the synthesis of the core proteins that ultimately converts sunlight into the chemical energy that produces oxygen and organic matter. Recent insights into the mito- and chlororibosomes have provided the first glimpses into the distinct and specialized machineries that involved in synthesizing almost exclusively hydrophobic membrane proteins. Our findings showed: 1) mitoribosomes have different exit tunnels, intrinsic GTPase in the head of the small subunit, tRNA-Val incorporated into the central protuberance; 2) chlororibosomes have divaricate tunnels; 3) ribosomes from both organelles exhibit parallel evolution. This allows contemplation of questions regarding the next level of complexity: How these ribosomes work and evolve? How the ribosomal components imported from cytosol are assembled with the organellar rRNA into a functional unit being maturated in different compartments in organelles? Which trans-factors are involved in this process? How the chlororibosomal activity is spatiotemporally coupled to the synthesis and incorporation of functionally essential pigments? What are the specific regulatory mechanisms?
To address these questions, there is a need to first to characterize the process of translation in organelles on the structural level. To reveal molecular mechanisms of action, we will use antibiotics and mutants for pausing in different stages. To reconstitute the assembly, we will systematically pull-down pre-ribosomes and combine single particle with tomography to put the dynamic process in the context of the whole organelle. To understand co-translational operations, we will stall ribosomes and characterize their partner factors. To elucidate the evolution, we will analyze samples from different species.
Taken together, this will provide fundamental insights into the structural and functional dynamics of organelles.
Fields of science
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Funding Scheme
ERC-STG - Starting GrantHost institution
10691 Stockholm
Sweden