1. Department of Biochemistry/MS200, University of Nevada, Reno, Nevada 89557–0014 (E.W.C., J.C.C); Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts 02114 (O.R.P); Department of Biochemistry, University of Wisconsin Biotechnology Center, Madison, Wisconsin 53706 (A.H.); and School of Biology, University of Newcastle, Newcastle upon Tyne NE1 7RU, United Kingdom (