Institution: | 1 Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, Evanston, IL 60208-3500, USA 2 Department of Biochemistry and Biophysics, School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6059, USA 3 Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104-6059, USA 4 Department of Structural Biology, Stanford University, Palo Alto, CA 94305-5126, USA 5 Howard Hughes Medical Institute, Northwestern University, Evanston, IL 60208-3500, USA |