[1] CALTECH, Div Biol, Pasadena, CA 91125 USA
[2] CALTECH, Howard Hughes Med Inst, Pasadena, CA 91125 USA
[3] GlaxoSmithKline, Dept Computat & Struct Sci, King Of Prussia, PA 19406 USA
[4] Purdue Univ, Dept Biochem, W Lafayette, IN 47907 USA
[5] Millennium Pharmaceut, Cambridge, MA 02139 USA