[1] Univ Calif Riverside, Dept Bioengn, Riverside, CA 92521 USA
[2] Univ Calif San Diego, Dept Pharmacol, San Diego, CA 92103 USA
[3] Univ Calif Berkeley, Dept Mol Biol, Berkeley, CA 94720 USA
[4] Univ Kansas, Lawrence, KS 66045 USA
[5] Univ Zurich, Zurich, Switzerland
[6] Univ Calif Berkeley, Dept Mol Cell Biol, Berkeley, CA 94720 USA
[7] Univ Calif San Diego, Chem & Biochem, La Jolla, CA 92093 USA