Studying translation by Cryo-Electron Microscopy: Investigating intact mitochondria and isolated ribosomes of humans, algae and plants by cryoEM

Abstract

In this thesis, we employ cryoET to investigate mitoribosomes inside isolated human mitochondria and cell sections of green algae. The findings shed light on the molecular evolution of mitoribosomes and visualize the structure of the human mitoribosome inside intact mitochondria at unprecedented resolution. This allowed us to resolve a previously unidentified binding interface of the mitochondrial protein insertase and identify the presence of a hitherto uncharacterized alternative insertase-complex. In addition, the structure of the sucrose-arrested plant ribosome was determined by SPA. The structure allowed for the identification of the sucrose binding site, depicting the first case of a metabolite-binding site for a eukaryotic ribosome. Surprisingly, the binding site is functionally conserved across humans, plants and bacteria. The findings in this thesis provide novel insights into mitochondrial protein synthesis and metabolite-induced translational regulation of eukaryotes.