Structural biology of glutamate receptor ion channel complexes

•Resting active and desensitized state AMPA and kainate receptor structures.•First structure of an AMPA receptor TARP complex.•NMDA receptors adopt unexpected conformations. Chemical transmission at excitatory synapses in the brain is mediated by a diverse family of glutamate receptor ion channels (iGluRs), tetrameric membrane protein assemblies of molecular weight 400–600kDa. Until recently, structural information for intact iGluRs was limited to biochemically tractable homomeric receptors trapped in different conformational states. These provided key insights into the mechanisms of iGluR activation and desensitization. Structures of heteromeric AMPA and NMDA receptors, the major iGluR families in the brain, together with long awaited cryo-EM structures of an AMPA receptor TARP complex, expand this picture and reveal surprising conformational diversity, raising many fundamental and controversial questions.