1. Department of Biochemistry, College of Agricultural and Life Sciences,1 and
2. Institute for Molecular Virology2 and
3. Department of Biological Sciences, Purdue University, West Lafayette, Indiana 479073; and
4. Integrated Microscopy Resource,4 The Graduate School, University of Wisconsin—Madison, Madison, Wisconsin 53706;
5. Department of Microbiology, University of Minnesota Medical School, Minneapolis, Minnesota 554555