Periodic Reporting for period 4 - ComplexAssembly (The birth of protein complexes)
Reporting period: 2022-07-01 to 2023-01-31
Proteins constitute the individual building blocks of life on the molecular level. They are often gathered into physically associated groups of multiple proteins, so-called protein complexes that form the major functional units inside of living cells. Faithful protein complex assembly is fundamentally important for cellular homeostasis but little is known about the very transient molecular events that occur during the early steps of this process. This project aims to understand the order in which protein complexes are assembled, to investigate if this physical association already occurs during protein synthesis and to visualize the transient intermediates of assembly. The knowledge generated during this project will be of high relevance for scenarios under which a cell’s protein quality control system has to cope with stress, such as aging and neurodegenerative diseases. It might also facilitate the more efficient industrial production of therapeutically relevant proteins.
We have worked on method development for the identification of proteins that associate with each other already during synthesis and for the visualization of protein complex assembly intermediates. We applied these methods to the nuclear pore complex, one of the most intricate protein complexes. We have, at least in part, determined the order in which the individual proteins that constitute these complexes are assembled. We identified a subset of components that is synthesized directly at the sites of biogenesis, implying physical association during synthesis. We furthermore found that importins may bind to nascent cargos already at the exit tunnel of the ribosome.
We found that the order of assembly is context-dependent. In this particular case, it differs during oogenesis and early embryogenesis as compared to somatic cells. We focus our efforts on the more precise elucidation of the early steps of assembly and the visualization of intermediates. We furthermore found a chaperoning role of importins during protein complex formation.