1Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
2Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115 USA
3Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115 USA
4Biotechnology-Bioservices Center, University of Connecticut, Storrs, CT 06269, USA
5Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA