Abstract
Actin is essential for key processes in all eukaryotic cells. Cellpermeable optojasps provide spatiotemporal control of the actin cytoskeleton, confining toxicity and potentially rendering F-actin druggable by photopharmacology. Here, we report cryo electron microscopy (cryo-EM) structures of both isomeric states of one optojasp bound to actin filaments. The high-resolution structures reveal for the first time the pronounced effects of photoswitching a functionalized azobenzene. By characterizing the optojasp binding site and identifying conformational changes within F-actin that depend on the optojasp isomeric state, we refine determinants for the design of functional F-actin photoswitches.