Detection of a conformational change in G gamma upon binding G beta in living cells

Interaction induced changes in the conformation of proteins are frequently the molecular basis for the modulation of their activities. Although proteins perform their functions in cells, surrounded by many potential interaction partners, the studies of their conformational changes have been mainly restricted to in vitro studies. Ste4p (G beta) and Ste18p (G gamma) are the subunits of a heterotrimeric G-protein in the yeast Saccharomyces cerevisiae. A split-ubiquitin based conformational sensor was used to detect a major structural rearrangement in Ste18p upon binding to Ste4p. Based on these in vivo results and the solved structure of the mammalian G beta gamma, we propose that G gamma of yeast adopts an equally extended structure, which is only induced upon association with G beta.