Visualizing protein interactions by bimolecular fluorescence complementation in Xenopus

Bimolecular fluorescence complementation (BiFC) provides a simple and direct way to visualise protein–protein interactions in vivo and in real-time. In this article, we describe methods by which one can implement this approach in embryos of the South African claw-toed frog Xenopus laevis. We have made use of Venus, an improved version of yellow fluorescent protein (YFP), so as to achieve rapid detection of protein interactions. To suppress spontaneous interactions between the N- and C-terminal fragments of Venus, a point mutation (T153M) was introduced into the N-terminal fragment. We have used this reagent to monitor signalling by members of the transforming growth factor type β family in cells of the Xenopus embryo.