TULIPs: tunable, light-controlled interacting protein tags for cell biology.
                            
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                                TULIP
                            
                            
                                
                                    HeLa
                                
                            
                                
                                    in vitro
                                
                            
                                
                                    S. cerevisiae
                                
                            
                            
                                Signaling cascade control
                            
                                Control of cytoskeleton / cell motility / cell shape
                            
                                Cell cycle control
                            
                            
                            
                            
                            
                        
                        
                        
                        
                            Abstract:
                            Naturally photoswitchable proteins offer a means of directly manipulating the formation of protein complexes that drive a diversity of cellular processes. We developed tunable light-inducible dimerization tags (TULIPs) based on a synthetic interaction between the LOV2 domain of Avena sativa phototropin 1 (AsLOV2) and an engineered PDZ domain (ePDZ). TULIPs can recruit proteins to diverse structures in living yeast and mammalian cells, either globally or with precise spatial control using a steerable laser. The equilibrium binding and kinetic parameters of the interaction are tunable by mutation, making TULIPs readily adaptable to signaling pathways with varying sensitivities and response times. We demonstrate the utility of TULIPs by conferring light sensitivity to functionally distinct components of the yeast mating pathway and by directing the site of cell polarization.