Dr. Emma Fenech, Zentrum für Biochemie, Universität zu Köln

The endoplasmic reticulum (ER) membrane coordinates a multitude of diverse and essential functions. The range and robustness of each function is upheld by the presence of parallel or homologous machineries. Each machinery forms functional units through stable interactions with their cofactors and transient interactions with substrates and regulators. The nature of transient interactors has made them much more challenging to identify, and while the advent of proximity-labelling techniques promised to tackle this problem, these methods lagged behind in the model eukaryote, Saccharomyces cerevisiae. To overcome this, we created a bespoke system for enhancing transient interactor discovery and optimised robust proximity-labelling protocols in yeast. I will expand on how these approaches were used to uncover novel substrates of the ER insertase complex (EMC) and proteins proximal to each of the six LAM homologs resident at various ER membrane contacts. To make these tools available for systematic probing of functional interactions, we generated five full-genome collections of strains in which every yeast protein is tagged with different proximity-labelling systems. I will share how these comprehensive toolkits can be used and developed to uncover mechanistic details into how homologous membrane machineries confer plasticity and specificity to each ER function. Collectively, these technologies will bring us closer to mapping the complete functional landscape of this organelle.