Characterizing Protein-Protein Interactions Using Mass Spectrometry: Challenges and Opportunities.

During the past decades, mass spectrometry (MS)-based proteomics has become an important technology to identify protein-protein interactions (PPIs). The application of a quantitative filter in protein enrichments from crude lysates to discriminate bona fide interactors from background proteins has proved to be particularly powerful. Recently, many different approaches to identify PPIs have been developed, including proximity-ligation technology and global interactome profiling based on the co-behavior of protein complexes in biochemical purification or perturbation experiments. Furthermore, methodologies have been introduced that provide information regarding the stoichiometry and topology of detected PPIs. We review these novel methodologies and emphasize the need to miniaturize workflows to analyze protein interactions in biological and pathological contexts where sample amounts are limited.