Provided herein is an isolated fusion protein comprising a light-responsive domain and a heterologous peptide component. Exposure of the fusion protein to light induces a conformational change in the fusion protein that alters an activity of the fusion protein and the activity is a binding activity selected from an in vitro binding activity, an in vivo extracellular binding activity and an in vivo intracellular binding activity. Also provided are methods of using and identifying the fusion proteins.