How amyloid can be a substrate of memory Formation of memories requires changes in the molecular composition of the synapse. How these changes occur and what maintains this altered synaptic composition so that memory can persist are unknown. Hervas et al. report the structure of a synaptic translation regulator called Orb2 isolated from the brains of adult fruit flies that is important for the maintenance and recall of memory. Orb2 forms an amyloid and changes its activity from a translation repressor to an activator. The amyloid core is composed of polar hydrophilic residues, as opposed to the hydrophobic ones found in nonfunctional or pathological amyloids. The structure provides insights into how amyloids could be a stable yet malleable substrate of memory. Science , this issue p. 1230