Using yeast as a model to study membrane proteins

Purpose of review Many cellular processes are controlled via either stable or transient protein-protein interactions (PPIs). Protein complexes are 'molecular machines' in which multiple interactive partners carry out various cellular functions. Given that almost a third of the proteome consists of membrane proteins and that more than 50% of currently available drugs are targeted toward them, investigation of membrane protein complexes has taken center stage over the past years. Thus, gaining an in-depth understanding of PPI networks will give us more insight into the functional relationship as well as downstream effectors of protein complexes, hence opening strategies for new drug target definitions. Recent findings Studying membrane proteins in yeast has recently been applied to many different classes of proteins with diverse functions and structures including membrane transporters. Techniques such as the split-ubiquitin membrane yeast two-hybrid or variants of the protein-fragment complementation assay have been successfully applied to both large-scale genome-wide screens and as smaller-scale PPI studies in a reliable and robust fashion. Summary Yeast-based methods to study membrane PPI in vivo offer a powerful tool for the investigation of protein complexes from various organisms, including mammals. The investigation of global protein maps will serve as a foundation for mechanistic and quantitative studies of poorly characterized gene products and disease-associated proteins. Identification of PPIs is also of great interest for drug discovery as many human diseases result from abnormal PPIs.