The yeast two-hybrid (Y2H) method was developed by Stan Fields and has been used in many labs to detect protein-protein interactions. Although it is not a perfect method, it does allow high throughput screening of protein interactions which is one critical component of proteomics.
Embedded below is a QT movie showing how the Y2H method
was originally developed to produce a colored product to indicate two
proteins (bait and prey) were interacting. You may control the movie
using the controls under the images.