[1] Scripps Res Inst, Dept Chem, Dept Integrat Struct & Computat Biol, La Jolla, CA 92037 USA
[2] Scripps Res Inst, Skaggs Inst Chem Biol, La Jolla, CA 92037 USA
[3] New York Struct Biol Ctr, Simons Electron Microscopy Ctr, Natl Resource Automated Mol Microscopy, New York, NY 10027 USA
[4] Columbia Univ, Dept Biochem & Mol Biophys, 630 W 168th St, New York, NY 10032 USA
[5] Salk Inst Biol Studies, Genet Lab, 10010 N Torrey Pines Rd, La Jolla, CA 92037 USA
[6] Salk Inst Biol Studies, Helmsley Ctr Genom Med, 10010 N Torrey Pines Rd, La Jolla, CA 92037 USA