We thank R. Axel, R. MacKinnon, B. Noro and L. Vosshall for advice on the manuscript, A. Siliciano and C. Monnier for technical advice and preliminary biochemistry, other members of the Ruta laboratory for discussions, and R. Boggavarapu for help with initial negative-stain EM experiments. We are grateful to M. Ebrahim and J. Sotiris at The Rockefeller University Evelyn Gruss Lipper Cryo-Electron Microscopy Resource Center for assistance with microscope operation, F. Weis-Garcia and S. L. Bourne at the MSKCC Antibody & Bioresource Core Facility for hybridoma generation, and R. Lavoisier and C. Adura at The Rockefeller University High Throughput & Spectroscopy Resource Center for support on functional assays. This work was supported by a Helmsley Postdoctoral Fellowship (to K.H.K.) and a Sinsheimer Foundation Award, the National Institutes of Health (R01-AI103171-01A1) and New York Stem Cell Foundation Robertson Neuroscience Investigator Award (to V.R.).

Reviewer information

Nature thanks R. Benton, E. Gouaux and the other anonymous reviewer(s) for their contribution to the peer review of this work.