Abstract: The present invention provides methods and related vectors and host cells for quantitative analysis of protein interactions in eukaryotic expression system. More specifically, the invention provides a yeast surface two-hybrid (YS2H) system that can express a pair of proteins, one protein (“bait”) as a fusion to a yeast cell wall protein, and the other (“prey”) in a secretory form. When two proteins interact in this system, they associate in the secretory pathway, and the prey that would otherwise be released into the media is captured on the cell surface by the bait. Expression of the bait and the prey proteins can be designed to promote a synchronized and comparable level of expression.