1. Department of Chemical Physiology and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
2. Division of Cell Biology, La Jolla Institute for Allergy and Immunology, 9420 Athena Circle, La Jolla, CA 92037, USA.
3. Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, CA 92037, USA.