Use of G-protein fusions to monitor integral membrane protein-protein interactions in yeast

The control of protein-protein interactions is a fundamental aspect of cell regulation. Here we describe a new approach to detect the interaction of t wo proteins in vivo. By this method, one binding partner is an integral mem brane protein whereas the other is soluble but fused to a G-protein gamma-s ubunit. If the binding partners interact, G-protein signaling is disrupted. We demonstrate interaction between known binding partners, syntaxin 1a wit h neuronal Sec1 (nSec1), and the fibroblast-derived growth factor receptor 3 (FGFR3) with SNT-1. In addition, we describe a genetic screen to identify nSec1 mutants that are expressed normally, but are no longer able to bind to syntaxin la. This provides a convenient method to study interactions of integral membrane proteins, a class of molecules that has been difficult to study by existing biochemical or genetic methods.