Diversity in ion channel complexes AMPA receptors are glutamate activated ion channels that mediate fast synaptic transmission in the nervous system and play a key role in learning and memory. The receptors are tetramers built from various combinations of four subunits, with functional diversity coming from the range of subunit compositions. Zhao et al. purified native receptors from rat brains and determined the structures of 10 different complexes by cryo–electron microscopy. Certain arrangements of the four subunits are preferred. The structure of a key gating element—a linker between the transmembrane and ligand binding domains—reveals how this receptor may function. Science , this issue p. 355