Abstract
Molecular switches have been instrumental in the development of powerful and versatile genetic tools for directly probing biochemical processes, such as intracellular signaling, within their native contexts. A molecular switch can be broadly defined as a molecular system capable of existing in either of two states (e.g., conformations), which can be converted from one state to the other by a specific input stimulus. This protocol outlines a method for using a kinase-inducible bimolecular switch, along with live-cell fluorescence microscopy, to directly control and monitor the activity of a specific enzyme in living cells.