[1] Univ Calif San Diego, Howard Hughes Med Inst, La Jolla, CA 92093 USA
[2] Univ Calif San Diego, NSF, Ctr Theoret Biophys, Dept Chem & Biochem, La Jolla, CA 92093 USA
[3] Mayo Clin, Coll Med, Receptor Biol Lab, Dept Physiol & Biomed Engn, Rochester, MN USA
[4] Univ Calif San Diego, Dept Pharmacol, La Jolla, CA 92093 USA