Yeast substrate-trapping system for isolating substrates of protein tyrosine phosphatases.

Protein tyrosine phosphorylation, controlled by the activities of both protein tyrosine kinases (PTKs) and protein tyrosine phosphatases (PTPs), plays critical roles in a wide variety of cellular events. However, in contrast to the PTKs, our understanding of the biological functions of PTPs has been limited to date. This is mainly the result of the difficulty in identifying the substrate molecules of individual PTPs. We described a genetic method to screen for PTP substrates, which we have named the "yeast substrate-trapping system." This method is based on the yeast two-hybrid system with two essential modifications: the conditional expression of a PTK to tyrosine-phosphorylate the prey protein, and screening using a substrate-trap PTP mutant as bait. This system is conceptually applicable to all the PTPs, because it is based on PTP-substrate interaction in vivo, namely the substrate recognition of individual PTPs. The identification of physiological substrates will shed light on the physiological functions of individual PTPs.